University:
Auburn University
Course:
BIOL 3500 | Perspectives in Immunology
Academic year:

2021
Views:

458

Pages:

300
Author:

Rhoebi

Immunology course lecture The role of the immune system: to protect the organism from external and internal foreign substances Autoimmune diseases: the body mounts an immune response against self structures More than 100 illnesses are autoimmune E.g. rheumatoid arthritis, multiple sclerosis, gluten sensitivity, type I. (juvenile) diabetes mellitus • Specific unresponsiveness of the immune system to a particular antigen that is actively induced by the antigen • Immunodeficiency: impaired responsiveness to all antigens (e.g. AIDS) • Immunosuppression: impaired responsiveness to all antigens is intentionally generated (generally by drugs) Normal immune response  Antigen: immunogen  Recognition: antigenpresenting cells  Immune response: reactive lymphocytes, antibodies, cytokines, etc  Result: elimination of the pathogen or the altered self Immune response during tolerance • Antigen: tolerogen • Recognition: antigen-presenting cells • Immune response: regulatory Tlymphocytes, blocking antibodies, antiinflammatory cytokines, etc. • Result: tolerance of the self antigen Autoimmune response  Antigen: autoantigen  Recognition: antigen-presenting cells  Immune response: autoreactive lymphocytes, autoantibodies, cytokines, etc.  „Result”: destruction of the target organ The „hardware” is the same, the „software” (regulation) is different  Central tolerance  T-cells in the thymus, B-cells in the bone marrow: learn how to tolerate self  Peripheral tolerance  Mature lymphocytes (already in the circulation or the tissues) become tolerant to a given antigen after encountering it The receptors of lymphocytes (T and B) are not pre-manufactured, but are continuously been constructed from basic parts (like a puzzle) (somatic recombination) AIRE – autoimmun regulator A regulatory protein – crucial part of a transcriptional complex – induces the „promiscuous” expression of a multitude of proteins in the mTEC The receptors of lymphocytes (T and B) are not pre-manufactured, but are continuously been constructed from basic parts (like a puzzle) (somatic recombination) APECED: autoimmunity, polyendocrinopathy, candidiasis, ectodermal dysplasia Only those thymocytes (early , immature T-cells) survive who are able to bind the self MHCantigen complex But: if the binding is strong to the MHC + self antigen complex → apoptosis…  Apoptosis (clonal deletion) ~ Burnet’s clone- selection theory  Clonal anergy (anergic cells proceed to the periphery  Transformation to regulatory T-cells  B-cells: receptor editing In response to the recognition of self MHC + self antigen, T-cells can evolve into natural regulatory T-cells (nTreg) with suppressive activities. Phenotype: CD4+ CD25+ FoxP3+ Function: activated in response to antigenic stimuli – memóry cell formation is possible – possess inhibitory function and activities Huehn J, Nat Rev Immunol 2009 FoxP3-deficiency: IPEX syndrome: immune dysregulation, polyendocrinopathy, enteropathy, X-linked Dario AA, Nat Rev Immunol 2008  20-30% of the lymphocytes leaving the thymus are autoreactive  Why do not they activate?  Double signal  Double signal  Danger signals  PAMP: pathogen-associated molecular pattern – bind to pattern recognition receptors (toll-like receptor (TLR), nod-like receptor (NLR), etc)  DAMP: damage-associated molecular pattern (heat shock proteins, HMGB-1, extracellular matrix degradation products, etc.)  Activate dendritic cells and other antigen-presenting cells (APC)  Normal apoptosis → tolerogenic dendritic cell  If the T-cells meet the antigen without co- stimulation, they die with apoptosis or are rendered anergic  Induced regulatory T-cells Natural Treg Induced Treg-s TGF-β IL-10 Microenvironment (gut, respiratory mucosa, TGF-β) Tolerogenic dendritic cells Suboptimal activation signal Lymph node 1. Checkpoint No 1: bone marrow Positive selection Negative selection Clonal deletion Receptor editing Clonal anergy Centrum germinativum IgG IgM Plassmasejt IgG Memória B sej Forrás: Cancro MP et al. J Clin Invest. 2009;119:1066-73. 2. Checkpoint No 2: spleen (transitional cells) The deletion of anergic autoreactive cells Balance: The size of the B-cell repertoire vs elimination of autoreactive B-cells 19 Forrás: Cancro MP, J Clin Invest 2009;119:1066-1072 20  T- and B-lymphocytes reactive with every self structure     (antigenic determinant) do develop in the normal organism Most of these autoreactive cells are eliminated (deletion) The rest will circulate in the peripheral lmyphoid organs and the tissues, react with the self structures, but will not be activated (anergic cells or natural regulatory cells, or peripheral (induced) regulatory cell Regulation is crucial (appropriate functioning of the thymus and bone marrow, the site, concentration, tissue microenvironment, and the mode of the antigen-presentation – dendritic cell The (appropriately regulated) autoreactivity is a necessary process – e.g. the recognition of foetal antigens is vital to the survival of the foetus (sufficient difference between the maternal and paternal MHC-repertoire Theofilopoulos AN, Nature Immunol 2017 • Molecular mimicry • Altered autoantigen – Structure (post-translational modification – e.g. citrullination, protein cleavage) – Localisation (uveitis, Sjögren’s, ANCA-vasculitides) • The autoantigen is regarded as dangerous – Parallel infection or tissue damage • Inherent hyperactivity or decreased threshold of the immune cells (SLE) RA genetic susceptibility loci identified to date, and cumulative proportion of observed variance in disease susceptibility explained thus far Viatte, S. et al. (2013) Genetics and epigenetics of rheumatoid arthritis Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2012.237 Kallberg et al Am J Hum Genet 2007;80:867–75) • Peptidyl arginine deminase (PAD) – In humans: PAD1, 2, 3, 4 (=5), 6 • Physiologically: epidermis, central nervous system • Pathologically: especially at sites of inflammation • In RA: lung, gingiva – smoking-induced bronchitis, gingivitis • Synovial lining and sublining – PAD2 and 4 – macrophages, lymphocytes – occurs in arthritis of any cause, including even trauma Source: www.hopkinsarthritis.org • The severity of periodontal disease correlates with disease activity of RA Kobayashi T, J Periodontol 2010 • Antibiotic or dental treatment of periodontitis reduces RA disease activity Ortiz P, J Periodontol 2009 • Severe periodontal disease diminishes the therapeutic efficacy of anti-TNF therapy of RA Savioli C, J Clin Rheum 2012 • Anti-TNF therapy may improve periodontitis Mayer Y, J Periodontol 2009 • Alveolar bone loss is parallel with juxtaarticular bony erosions of RA patients Marotte H, Ann Rheum Dis 2006  Anaerobic rod-shaped bacterium  Rarely present in periodontally healthy individuals  Its colonization in the periodontal sac is necessary for the development of periodontitis  Unique among prokaryotes for expressing PAD Citrullinated proteins are present in the gingiva of a patient with periodontitis Lundberg, K. et al. (2010) Periodontitis in RA—the citrullinated enolase connection Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2010.139 A schematic model of initiation of RA-associated immunity against citrullinated proteins in the lungs Catrina, A. I. et al. (2014) Lungs, joints and immunity against citrullinated proteins in rheumatoid arthritis Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2014.115 Source: http://chemistry.berea.edu/~biochemistry/2009/Jacob/  Highly specific for RA  Rare (< 5%) in patients with chronic bronchitis, gingivitis, lung cancer or with other systemic autoimmune diseases  ACPA-s appear several years (usually 10 or more) before RA onset  Shared epitope carriage greatly promotes the induction of ACPA-s Schematic illustration of the etiological hypothesis for P. gingivalis and citrullinated α-enolase involvement in RA Lundberg, K. et al. (2010) Periodontitis in RA—the citrullinated enolase connection Nat. Rev. Rheumatol. doi:10.1038/nrrheum.2010.139 • Molecular mimicry • Altered autoantigen – Structure (post-translational modification – e.g. citrullination, protein cleavage) – Localisation (uveitis, Sjögren’s, ANCA-vasculitides) • The autoantigen is regarded as dangerous – Parallel infection or tissue damage • Inherent hyperactivity or decreased threshold of the immune cells (SLE) Apoptotic products (nucleosome…) normally do not activate the dendritic cells, but even induce tolerogenic dendritic cells → Treg cell formation In SLE, they do activate them (why?: impaired apoptotic mechanisms? Defect in the clearance of apoptotic products? An increased propensity of dendritic cells to produce interferon-α? Enhanced toll-like receptor-9 (TLR9) activation? Fehr EM, J Autoiomm 2012 In SLE patients, there is an overproduction of interferon-α („interferonsignature”) Inducers of IFN-α: RNA, DNA (through toll-like receptors) Producers of IFN-α: dendritc cells (mainly plasmacytoid dendritic cells) Effects of IFN-α: T-cell activation, T-cell-dependent B-cell activation In SLE (and also in Sjögren’s syndrome) BAFF (BLyS) production is increased B-cells (also the autoreactive ones) receive an exaggerated survival signal  Genetic predisposition ◦ ◦ ◦ ◦ Almost always polygenic Rarely monogenic (APECED, IPEX) The risk of inheriting a disease is variable Often there is an association of multiple autoimmune diseases in one patient  Environmental trigger ◦ ◦ ◦ ◦ Viral or other infection UV light Smoking Nutrient (e.g. gluten in flour)  Tissue damage, hormonal background, neuro-psychiatric factors Tumorimmunology Krisztina Buzas, Ph. D. Univ. Of Szeged, Department of Immunology Definitions Tumor ¥ ¥ ¥ A tumor is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer. While cancer is by definition malignant, a tumor can be benign, pre-malignant, or malignant, or can represent a lesion without any cancerous potential whatsoever. The terms "mass" and "nodule" are often used synonymously with "tumor". Generally speaking, however, the term "tumor" is used generically, without reference to the physical size of the lesion. Tumor Definition: Unregulated cell proliferation benign: unlimited growing potencial NO metastases malignant: unlimited growing potential metastasis formation Types of cancer ¥ Carcinoma: tumors arising from epithelial tissue, such as glands, breast, skin, and linings of the urogenital, digestive, and respiratory systems, representing 89.3% of all cancers. ¥ Lymphoma, Myeloma: diseases of the lymph nodes and spleen that cause excessive production of lymphocytes (5.4% of cancers) ¥ Leukemia: disease of bone marrow causing excessive production of leukocytes (3.4% of all cancers) ¥ Sarcoma: solid tumors of muscles, bone, and cartilage that arise from the embryological mesoderm; they represent 1.9% of all cancers. Necessary conditions of tumor formation Properities of transformed cells Molecular basis of cancer Radioactivity Chemicals Viruses Mutations or changing in gene expression Unlimited cell proliferaton Proto-oncogenes alter to oncogens Inhibition of Tumor-supressor genes P53, retinoblastome Induction of tumor formation Carcinogens ¥ A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. ¥ Several radioactive substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example gamma rays alpha particles, which they emit. ¥ Chemicals: Dioxins and dioxin-like compounds, benzene, kepone, and asbestos have all been classified as carcinogenic agents. Industrial smoke and tobacco smoke were identified as sources of dozens of carcinogens, including benzo[a]pyrene, tobacco-specific nitrosamines such as nitrosonornicotine, and reactive aldehydes such as formaldehydeÑwhich is also a hazard in embalming and making plastics. Vinyl chloride, from which PVC is manufactured, is a carcinogen and thus a hazard in PVC production. Co-Carcinogens ¥ Co-carcinogens are chemicals that do not necessarily cause cancer on their own, but promote the activity of other carcinogens in causing cancer. ¥ Some virus are co-carcinogens like Herpesviruses, EpsteinÐBarr virus and human herpesvirus 4 (HHV-4). ¥ Over intake beta carotene for a long period of time increased the risk of lung cancer, prostate cancer and many other kind of malignant tumor for cigarette smoker and worker having high contact with asbestos. Tumors, induced by different carcinogens ¥UV-induced tumors: ¥ Melanoma: metastatic ¥ Non-melanoma cancers: ¥ ¥ Basal cell carcinoma: rarely spreads Squamous cell carcinoma: can spread ¥Chemically-induced tumors: ¥ Free radicals and other oxidants steal electron from DNA and cause cancer ¥Virally-induced cancers: highly immunogenic: ¥ ¥ DNA viruses: HPV and cervical cancer RNA viruses: HTLV and T cell leukemia Carcinogenesis Oncoviruses ¥ Generally, tumor viruses cause little or no disease after infection in their hosts, or cause non-neoplastic diseases such as acute hepatitis for hepatitis B virus or mononucleosis for Epstein-Barr virus. A minority of persons (or animals) will go on to develop cancers after infection. ¥ Types: ¥ 1. DNA viruses ¥ 2. RNA viruses Carcinogen viruses Oncogenic strategies of viruses Direct oncogenic viral mechanism involves either: ¥ insertion of additional viral oncogenic genes into the host cell or ¥ to enhance already existing oncogenic genes (proto-oncogenes) in the genome. Indirect viral oncogenicity involves chronic nonspecific inflammation occurring over decades of infection, as is the case for HCV-induced liver cancer. These two mechanisms differ in their biology and epidemiology: direct tumor viruses must have at least one virus copy in every tumor cell expressing at least one protein or RNA that is causing the cell to become cancerous. indirect tumor viruses can be lost from a mature tumor that has accumulated sufficient mutations and growth conditions (hyperplasia) from the chronic inflammation of viral infection. Metastases formation Metastases formation ¥ Metastasis, or metastatic disease (sometimes abbreviated mets), is the spread of a disease from one organ or part to another non-adjacent organ or part. ¥ Ability of metastases formation of 1cm3 tumor mass is 22%. ¥ Only 10% of cancer death caused by primary tumor Invasion-metastasis cascade Evolution of colonizing ability Tumorimmunity Crucial questions of tumorimmunology ¥ ¥ ¥ Actually, evidence is rapidly accumulating that the immune system does indeed contribute to the bodyÕs multilayered defenses against tumors. The difficulties associated with establising this type of anticancer defense are apparent from the outset: the immune system is organized to recognize and eliminate foreign agents from the body while leaving the bodyÕs own tissues unmolested. Cancer cells, however, are native to the body and are indistinguishable from the bodyÕs normal cells. How can cancer cells be recognized by the immune system as being different and, therefore, appropriate targets of immunmediated killing? Tumorantigens are neoantigens Abbas Tumorantigens 1. ¥ Antigens encoded by mutated genes ¥ neoantigens are produced by point mutations or deletions in genes that are unrelated to the development of the tumors. ¥ encoded proteins generate new MHC-binding peptides that are presented to T cells and are foreign to the immune system since they are not normally present. ¥ neoantigens are often cytosolic or nuclear proteins that are degraded by proteasomes and can be presented on class I major histocompatibility complex (MHC) molecules in tumor cells. ¥ After phagocytosis by dendritic cells, they may also enter the class II MHC antigen presentation pathway or be cross-presented by the class I pathway. Tumorantigens 2. ¥ Viral proteins expressed by tumor cells: ¥ Epstein-Barr virus (EBV), which is associated with B cell lymphomas and nasopharyngeal carcinoma ¥ human papillomavirus (HPV), which is associated with carcinomas of the uterine cervix, oropharynx ¥ In most of these DNA virusÐinduced tumors, virus-encoded protein antigens are found in the nucleus, cytoplasm, or plasma membrane of the tumor cells. Tumorantigens 3. ¥ Overexpressed cellular proteins Tumormarkers, tumorantigens ¥ A tumor marker is a substance found in the blood, urine, or body tissues that can be elevated in cancer, among other tissue types. ¥ Tumor markers may act as antigen to induce anti-cancer responses. Tumor markers ¥ Tumor specific markers ¥ Presented by cancer cells ¥ Tissue specific markers ¥ Presented by tumor-host tissue Well known tumor markers Oncologically application for diagnosis Tumormarkers Abbrevation Alfa-foetoprotein AFP Hepar cancer Cancer antigŽn 125 CA 125 Ovarium tumor Cancer antigŽn 15,3 CA 15,3 Breast cancer Cancer antigŽn 72,4 CA 72,4 Stomach cancer Cancer antigŽn 19,9 CA 19,9 Pancreatic cancer Carcinoembrion‡lis antigŽn CEA Cancer of digestive tract Neuronspecifikus enol‡z NSE Small cell lung cancer Prosztataspecifikus antigŽn PSA Prostate cancer Squamous cell carcinoma antigŽn SCC Squamous cell carcinoma Tissue polipeptid antigŽn TPA Lung cancer TPS Metastatic breast cancer Tissue polipeptid-specific antigŽn Cellular and humoral immunity Antitumoral effector mechanisms NK cell CTL Tumor cell Humoral Mechanisms Macrophage Kumar et al. Basic Pathology 6th ed. Figure 6-32 T cells Antigen derived mechanisms ¥ T cell mediated cytolysis ¥ Dendritic cells/APCs ¥ Macrophages ¥ B cell dependent mechanisms Dendritic cells Cytotoxic T lymphocyte (CTL) response against tumors ¥ Tumor antigens are picked up by host dendritic cells, and responses are initiated in peripheral (secondary) lymphoid organs. Tumorspecific CTLs migrate back to the tumor and kill tumor cells. Crosspresentation-CD8+ Tumor OR Tumor OR OR Transformated cell CD8+ T cell responses specific for tumor antigens may require crosspresentation of the tumor antigens by dendritic cells. PLEASE, REPEAT THE 3RD LECTURE, PART OF CROSSPRESENTATION (Dr. Czibula) CD8+ cell mediated cytotoxicity APOPTOSIS INDUCTION ¥ ¥ ¥ ¥ Perforin/granzyme B secretion, caspase 8 activation-complement system activation FasL expression, Fas and Death Receptor activation IFN-g induction CD4+ cells in anti-tumor response ¥ enhancing CD8+ T cell responses ¥ activating macrophages ¥ secretion of tumor necrosis factor and interferon-γ ¥ IFN-γ can increase tumor cell class I MHC expression and sensitivity to lysis by CTLs ¥ express granzyme B Macrophages Janus - the two-faced god=immunmechanisms in cancer In Roman religion and mythology, Janus is the god of beginnings and transitions, thence also of gates, doors, doorways, endings and time. He is usually a two-faced god since he looks to the future and the past. Macrophages are in the anti-cancer immunity The ãBeautyÓ and the ãBeastÓ in tumorimmunity Macrophage polarization Inducers: M1: LPS, bacterial compounds, tumor antigens M2a: IL-4, Il-13 M2b: TLR agonists M2c: Il.10, glucocortikoid hormons Direct killing T citotox, helper T reg NK Sup. DC B cell mediated anti-tumoral mechanisms Specific anti-tumoral responses, B cell mediated mechanisms ¥Derived by specific antibodies ¥ADCC ¥Complement activation ¥Opsonisation ADCC-antibody mediated mechanism Fc receptoros: CD16, CD32, CD64 Natural Killer cells Missing MHC-antigen does not needed Killing Mechanism ¥ Releasing secretoy vesicles ¥ Granzyme ¥ Perforin ¥ Fas ligand Escape Immune responses frequently fail to prevent the growth of tumors ¥ many tumors have developed specialized mechanisms for subverting host immune responses. ¥ tumor cells lose the expression of antigens that may be recognized by the host immune system. Even tumors that do elicit effective immune responses may become less immunogenic over time because subclones that do not express immunogenic antigens have a selective survival advantage. ¥ the rapid growth and spread of a tumor may overwhelm the capacity of the immune system to effectively control the tumor, which requires that all the malignant cells be eliminated. Tumorpromoting by immune cells ¥ Tumor associated macrophages (M2 phenotype) ¥ VEGF, MMP ¥ Innate immun cells-free radicals-DNA damage ¥ Mast cells, neutrophils, macrophages-soluble factors ¥ Th2 and Treg cells Evasion of immun responses-immune checkpoints ¥ Tumors evade antitumor T cell responses by engaging inhibitory molecules that normally function to prevent autoimmunity or regulate immune responses to microbes. ¥ PD-1 and CTLA-4 are often upregulated on tumor infiltrating T cells, consistent with their role in inhibiting tumor-specific T cell function ¥ Secreted products of tumor cells may suppress antitumor immune responses-TGF-beta ¥ Regulatory T cells may suppress T cell responses to tumors. ¥ Myeloid-derived suppressor cells (MDSCs) are immature myeloid precursors that accumulate in bone marrow, lymphoid tissues, blood, and tumors of tumor-bearing animals and cancer patients, and suppress innate and T cellÐmediated antitumor immune responses. How does a tumor escape immune surveillance by T cells? ¥ Generation of regulatory cells (CD4+CD25+ T cells) ¥ Secrete immunosuppressive molecules Ex: prostaglandins, transforming growth factor beta (TGF-b), interleukin-10 (IL-10), etc. 2MF F Tumor T regulatory CT L Soluble molecules Reverse death signal FasL Fas Tumor FasL Fas Tumor Apoptotic cell-Fas expressing cell CT L CT L Evasion of immun responses-loss of tumor antigens ¥ IMMUNOEDITING ¥ Immune responses to tumor cells impart selective pressures that result in the survival and outgrowth of variant tumor cells with reduced immunogenicity. ¥ selective survival of less immunogenic variant cells ¥ immune response directs changes in tumors that help them evade the response ¥ the antigen-negative tumor cells will have a growth advantage in the face of the host immune response Immunotherapies 1. Checkpoint Blockade Repeat the central and pripherial tolerance! 2. Vaccination ¥ Proinflammatory molecules are used to enhance the numbers of activated dendritic cells at the vaccination site. ¥ These adjuvants include Toll-like receptor (TLR) ligands, such as CpG DNA and mimics of dsRNA, and cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-12. ¥ Vaccination of tumor-bearing individuals with tumor antigens may result in enhanced immune responses against the tumor. ¥ Tumor antigens are delivered in the form of dendritic cell vaccines. In this approach, dendritic cells are purified from patients, incubated with tumor antigens, and then injected back into the patients. ¥ DNA vaccines and viral vectors encoding tumor antigens are being tested in clinical trials. Passive immunotherapies ¥ Passive antibody therapy involves the transfer of tumor-specific antibodies into patients, which is a rapid and theoretically very specific approach but does not lead to long-lived immunity. ¥ Some antitumor antibodies bind to cell surface molecules on tumor cells and engage host effector mechanisms that kill the tumor cells. These mechanisms include NK cell-mediated cytotoxicity, complement-mediated lysis, and complement- or Fc receptorÐ mediated phagocytosis by macrophages. Anti-CD20 is used for treating B cell lymphomas. ¥ Other monoclonal antibodies used in cancer therapy bind to growth factor receptors on cancer cells and interfere with the signaling required for tumor growth and survival. (Anti-Her2/Neu, anti-VEGF) Cytokine therapies ¥ Cancer patients can be treated with cytokines that stimulate the proliferation and differentiation of T lymphocytes and NK cells. ¥ ¥ enhance the activation of dendritic cells and tumor-specific CD8+ CTLs. ¥ to induce nonspecific inflammatory responses, which by themselves may have antitumor activity. IL-2 given intravenously, which has been effective in inducing measurable tumor regression in about 10% of patients with advanced melanoma and renal cell carcinoma ¥ IFN-α is approved for treatment of several cancers, including malignant melanoma, certain lymphomas and leukemias, and AIDSrelated Kaposi sarcoma. ¥ The mechanisms of the antineoplastic effects of IFN-α probably include inhibition of tumor cell proliferation CTLA-4 Žs PD-1 inhib’torok Immunol—giaiSzemle/ImmunologyQuarterly¥2017.IX.Žvfolyam,1.sz‡m Rajnavšlgyi ƒva Complementary and alternative medicine (CAM) ¥ https://www.nccih.nih.gov/ References ¥ ¥ ¥ ¥ Robert A. Weinberg: The Biology of Cancer Jeneway, Immunology Globocancer, WHO database Abbas Molecular Immunology 9. IMMUNE RESPONSES AGAINST EXTRACELLULAR AND INTRACELLULAR PATHOGENS. IMMUNESCAPE. Roberta Fajka-Boja Assistant professor University of Szeged, Department of Immunology 23.04.2021. REPEAT: • The structure of the immune system, lymphoid organs, barriers, SALT, MALT (1. lecture) • Innate immune system, cells, soluble elements, functions (2. lecture) • Antigen presentation (3. lecture) • T cell activation and effector functions (4. lecture) • B cell activation, antibody production and effector functions (5. lecture) • Inflammation, acute phase response (6. lecture) • The complement system (2. and 6. lecture) THE MAJOR TYPES OF PATHOGENS Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. PATHOGEN ENTRY POINTS AND BARRIERS Microbes can enter the host through breaches in the skin, by inhalation or ingestion, or by sexual transmission. Transmission of microbes: - Air, dust - Respiratory and oral secretion (talking, coughing, sneezing) - Physical contact - Indirect contact, with contaminated surfaces. - Transmitter: contaminated food, water, blood, faeces, urine… - By vectors (bites by fleas, ticks, mosquitoes…). Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. THE KINETICS OF IMMUNE RESPONSE AGAINST PATHOGENS The course of a typical acute infection that is cleared by the concerted action of innate and adaptive immune response: 1. Infection phase: Colonization and replication of the infectious agent. The innate response is initiated immediately following detection of the pathogen. 2. Inductive phase: when numbers of the pathogen exceed the threshold dose of antigen required for an adaptive response, the response is initiated. 3. Effector phase: after 4–7 days, effector cells and molecules of the adaptive response start to clear the infection. 4. Memory phase: after elimination of antigen, the immune response ceases, but antibody and immunological memory provide lasting protection against reinfection. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. IMMUNITY TO MICROBES Humoral immunity Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. Cellular immunity SENSING THE PATHOGENS: PATTERN RECOGNITION RECEPTORS Pattern recognition receptors are located in all the cellular compartments where pathogens may be present: - plasma membrane receptors detect extracellular pathogens, - endosomal receptors detect ingested microbes, - cytosolic receptors detect microbes in the cytoplasm. Pattern Recognition Receptors (PRR) bind Pathogen Associated Molecular Patterns (PAMP): e.g. Toll Like Receptors (TLR), NOD-Like Receptors (NLR), C-type lectin receptors, RIG-like receptors. Kumar, Abbas, Aster. Robbins Basic Pathology TOLL LIKE RECEPTORS (TLR) The plasma membrane TLRs recognize bacterial products such as lipopolysaccharide (LPS), and endosomal TLRs recognize viral and bacterial RNA and DNA. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. SIGNALLING PATHWAYS OF TOLL-LIKE RECEPTORS Ligand binding of TLRs induces signalling pathway which leads to activation of transcription factors. These increase gene expression, important for pathogen elimination and activation of the adaptive immune system. 1/ MYD88 (myeloid differentiation primary-response protein 88)-dependent signalling. Activation of NF-kB transcription factor, resulting in expression of inflammatory cytokines, chemokines, enzymes (COX, SOD, NOS), adhesion molecules, costimulatory molecules, antigen presentation. 2/ MYD88-independent signalling: Viral RNA binding to TLR3 activates the TRIF adaptor protein and the IRF3. Upregulation of type I. interferons (IFNα and β) and their anti-viral function. For example: Dendritic cells residing in the skin ingest microbes and their products and degrade them. Bacterial LPS induces changes in dendritic cells, stimulating them to migrate to lymph nodes and to initiate adaptive immunity by activating T cells. They change the character of their cellsurface molecules, increasing the number of MHC molecules on their surface and the expression of the co-stimulatory molecules CD80 (B7.1) and CD86 (B7.2). https://doi.org/10.3389/fimmu.2018.01027 Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. TYPE I INTERFERONS Type I interferons (IFN-α, IFN-β) are produced by virus-infected cells in response to intracellular TLR signaling and other sensors of viral RNA. Type I interferons bind to receptors on neighboring uninfected cells and activate signaling pathways, which induce expression of genes whose products interfere with viral replication. Type I interferons also bind to receptors on infected cells and induce expression of genes whose products enhance the cell’s susceptibility to CTL-mediated killing. PKR, Double-stranded RNA-activated protein kinase. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology EFFECTOR FUNCTIONS OF INNATE IMMUNE SYSTEM • Production of antimicrobial peptides. • Phagocytosis and killing of pathogens in phagosomes. • Degranulation, secretion of antimicrobial molecules (ROS, enzymes). • Production of cytokines, chemokines. • Cytotoxicity by NK cells. • Inflammation, acute phase response. • Activation of the complement system: opsonization, direct lysis, infammation. • Antigen presentation. Punt, Stranford, Jones, Owen: Kuby Immunology TYPE 1, TYPE 2, AND TYPE 3 IMMUNITY Cytokines and chemokines produced by pathogen-activated innate sensor cells (i.e., epithelial cells, tissue-resident mast cells, macrophages, and dendritic cells) initiate local inflammation, and also differentially activate ILCs (innate lymphoid cells) within the first hours of an infection. This early response acts to constrain pathogen entry at the initial site of infection to prevent dissemination while the adaptive response develops. Activated ILCs amplify and coordinate local innate responses and regulate the recruitment and maturation of different myelomonocytic innate effector cells (that is, granulocytes like neutrophils, eosinophils, and basophils, or monocytes) at the site of infection. Cytokines produced by ILCs may also guide the development of naive T cells into distinct effector subsets. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. RECOGNITION OF PATHOGENS BY ADAPTIVE IMMUNE SYSTEM Kumar, Abbas, Aster. Robbins Basic Pathology Antigen recognition requires specific antigen receptors: - B cell receptors (BCR) bind native antigen, - T cell receptors (TCR) bind antigenic peptides in complex with MHC. Punt, Stranford, Jones, Owen: Kuby Immunology THE NATURE OF ANTIGEN DETERMINES THE EFFECTOR HELPER T CELL RESPONSE Distinct effector T helper cell phenotypes are associated with different types of pathogens and immune-driven pathologies. A/ Th1 cells are associated with bacterial, protozoan, and viral infections, and promote microbicidal activity in macrophages. Similar pathways are invoked in some autoimmune diseases, where Th1 cells are directed against self-antigens. B/ Helminths and venoms drive Th2 cells that induce the release of toxic mediators from mast cells and eosinophils as well as promoting epithelial contractility and mucus production. M2 macrophages support tissue repair. Aberrant Th2 responses are strongly associated with allergic disease. C/ Extracellular bacterial and fungal infections drive Th17 cells that promote neutrophil activity and the release of anti-microbial peptides from the epithelium. Pathogenic Th17 cells are also associated with autoimmune diseases, such as multiple sclerosis and psoriasis. https://doi.org/10.1038/s41423-020-0465-0 IMMUNE EFFECTOR MODULES intracellular pathogens (bacteria, viruses, parasites) +opsonizing IgG isotypes (IgG1) multicellular parasites, or helminths +IgE extracellular bacteria and fungi +opsonizing IgG isotypes (IgG1) Each effector module includes subsets of innate sensor cells, ILCs, effector T cells, and antibody isotypes, which coordinate with subsets of circulating or tissue-resident myelomonocytic cells whose microbicidal functions they recruit and enhance. IMMUNOGLOBULIN ISOTYPES AND THEIR EFFECTOR FUNCTIONS IgM, all IgG, IgA IgG1, IgG3, IgG4, IgA IgG1, IgG3 IgM, IgG1, IgG3 Kumar, Abbas, Aster. Robbins Basic Pathology Activation of mast cells IgE, IgG1, IgG3 Immunoglobulin class switching takes place in germinal centres with the help of Tfh cells. Cytokines determine the isotype: e.g. IFNg → IgG; IL-4 → IgE; TGFb → IgA. Antibodies of different heavy-chain classes (isotypes) perform different effector functions. Fc RECEPTORS IN EFFECTOR FUNCTIONS AGAINST PATHOGENS • Fc-receptors (FcR) bind the Fc part of immunoglobulin heavy chains, if they are in complex with antigen (exept for high affinity FcRs). FcRs are isotype specific. • IgG binding receptors: - FcgRI (CD64): high affinity activating receptor, highest affinity for IgG1 and IgG3. Present on monocytes, macrophages, neutrophils, eosinophils, dendritic cells. Take part in phagocytosis of Ig-bound microbes, uptake of antigens, activation of oxidative burst, induction of killing. - FcgRIIa and FcgRIIc (CD32): medium affinity activating receptors on macrophages, neutrophils, eosinophils, Langerhans-cells, dendritic cells, thrombocytes. Mediates phagocytosis, degranulation, DC maturation and antigen presenting, thrombocyte aggregation. - FcgRIIb1 and FcgRIIb2 (CD32): inhibiting receptors. Regulate B cell activation and maturation of DC. Inhibits phagocytosis by macrophages and neutrophils. Continued…→ Erdei A, Sármay G, Prechl J: Immunológia - FcgRIIIa (CD16): low affinity activating receptor on macrophages, NK cells. Mediates ADCC (Antibody Dependent Cellular Cytotoxicity) of NK cells. - FcgRIIIb (CD16): low affinity activating receptor on macrophages, neutrophils, eosinophils and mast cells. Induce degranulation and extracellular killing of pathogens. - FcRn: neonatal Fc receptor, transports IgG through cells to reach different body compartments (fetus), increases half-life of IgG. https://bioprocessintl.com/sponsored-content/mitigate-risk-witheffector-function-characterization-for-antibody-therapeutics/ Continued…→ Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. Fc receptors and complement receptors synergize in inducing phagocytosis. Antibody coating induces activation of the complement system and the binding of complement components to the bacterial surface. Binding of Fc and complement receptors signals the phagocyte to increase the rate of phagocytosis, to fuse lysosomes with phagosomes, and to increase its bactericidal activity. • IgE binding receptors: - FcεRI: high affinity activating receptor on basophils, mast cells, activated eosinophils, mediates degranulation and production of inflammatory mediators. Binds free IgE. - FcεRII (CD23): on macrophages, eosinophils, follicular dendritic cells, Langerhans-cells, epithelial cells. Mediates degranulation and ADCC by IgE against multicellular pathogens, worms. ADCC • IgA binding receptors: - FcαR (CD89): mediates uptake by macrophages and granulocytes. eosinophil - polymeric immunoglobulin receptor (pIgR), present on the basolateral surfaces of the overlying epithelial cells, transports Erdei A, Sármay G, Prechl J: Immunológia dimer IgA and pentamer IgM through epithelium by transcytosis. Secretory component also protects the antibodies against cleavage by gut enzymes . IgA is synthesized by plasma cells in the lamina propria and transported into the lumen of the gut through epithelial cells at the base of the crypts. Dimeric IgA binds to the layer of mucus overlying the gut epithelium and acts as an antigen-specific barrier to pathogens and toxins in the gut lumen. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. IMMUNITY TO EXTRACELLULAR BACTERIA Extracellular bacteria are capable of replicating outside host cells, for example, in the blood, in connective tissues, and in tissue spaces such as the lumens of the airways and gastrointestinal tract. These bacteria induce inflammation, which results in tissue destruction at the site of infection. Second, bacteria produce toxins, which have diverse pathologic effects. Innate Immunity to Extracellular Bacteria -Phagocytes, inflammation -Complement system -ILC3 cells Adaptive Immunity to Extracellular Bacteria: -Immunoglobulin production (IgA, IgG) -Th17 cytokine production enhance the phagocytic and microbicidal activities of macrophages and neutrophils and stimulate antibody production. Punt, Stranford, Jones, Owen: Kuby Immunology ADAPTIVE IMMUNE RESPONSES TO EXTRACELLULAR MICROBES • Adaptive immune responses to extracellular microbes such as bacteria and their toxins consist of antibody production (A) and the activation of CD4+ helper T cells, which work via secreted cytokines (B) • Antibodies neutralize and eliminate microbes and toxins by several mechanisms. • Helper T cells produce cytokines that stimulate inflammation, macrophage activation, and B cell responses. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology TOXINS, SUPERANTIGENS, MITOGENS • Exotoxins: protein toxins produced and secreted by a bacterium. E.g: tetanus toxin - chronic muscle contraction, diphteria toxin - inhibits protein synthesis, cholera toxin - activates adenylate cyclase in intestinal epithelial cells, loss of water and electrolytes, botulinum toxin - blocks release of acetylcholine, leading to paralysis. • Superantigens are exotoxins, which bind directly to T-cell receptors and to MHC molecules. The superantigens (red bar) can bind to the Vβ domain of the T-cell receptor (TCR), away from the complementarity-determining regions, and to the outer faces of the MHC class II molecule, outside the peptide-binding site. They activate many T cells, with the subsequent production of large amounts of cytokines that can also cause a systemic inflammatory syndrome. SE: Staphylococcal enterotoxin and TSST-1: toxic shock syndrome toxin-1 from Staphylococcus aureus. • Endotoxins: Toxins derived from damaged bacterial cell walls. • Lipopolysaccharide (LPS): endotoxin from the cell wall of Gram-negative bacteria. Binding to TLR4 and CD14 on macrophages, it induces expression of inflammatory cytokines (fever, acute phase response, sepsis). It is a Tindependent antigen, binds both to the BCR and TLR on the B cells, thereby activates B-cells. Activates the alternative pathway of the complement system. T-independent antigen B-cell IMMUNITY TO INTRACELLULAR BACTERIA • A characteristic of facultative intracellular bacteria is their ability to survive and even replicate within phagocytes. Because these microbes are inaccessible to circulating antibodies, their elimination requires the mechanisms of cell-mediated immunity. E.g.: Mycobacterium tuberculosis, Mycobacterium leprae, Salmonella typhimurium, Listeria monocytogenes. • The innate immune response to intracellular bacteria consists of phagocytes and NK cells, interactions among which are mediated by cytokines (IL-12 and IFNg). Type 1 ILCs also defend against intracellular bacteria, secreting IFNg and TNF. • The typical adaptive immune response to these microbes is cell-mediated immunity, in which antigens are presented in MCH II complexes to T cells, and the effector Th1 cells activate phagocytes to eliminate the microbes. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology CYTOTOXIC RESPONSE TO INTRACELLULAR BACTERIA • Phagocytosed bacteria stimulate cytotoxic T cell responses if bacterial antigens are transported from phagosomes into the cytosol or if the bacteria escape from phagosomes and enter the cytoplasm of infected cells. • In the cytosol, the microbes are no longer susceptible to the microbicidal mechanisms of phagocytes, and for eradication of the infection, the infected cells have to be eliminated by CTL. • The macrophage activation that occurs in response to intracellular microbes may cause tissue injury, leading delayed-type hypersensitivity (DTH) reactions. Because intracellular bacteria often persist for long periods and cause inflammation, which may result in the formation of granulomas surrounding the microbes. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology THE ROLE OF IFNg IN RESPONSE TO INTRACELLULAR BACTERIA • Type II interferon. • It is produced by: Th1 cells, NK cells, Tc cells, • Activates macrophages: production of ROS and enzymes for intracellular killing, upregulation of MHC II expression, costimulatory molecules, cytokine (IL-12) production, to promote Th1 response. • Upregulation of NK cell cytotoxic activity. • Maturation of Tc cells to effector CTLs. • Promoting B cells isotype switching to IgG1 (opsonization, complement activation ADCC). • Upregulation MHC II expression of nonantigen presenting cells (endothelial cells). • Inhibiting Th2 type response, downregulating IL-4 and - 5. INDIVIDUAL DIFFERENCES IN THE RESPONSE AGAINST INTRACELLULAR BACTERIA • E.g: Mycobacterium leprae is able to persist and grow in macrophage vesicles and is normally restrained, but not cleared, by a type 1 host response. • Tuberculoid leprosy is manifested in patients who mount normal type 1 immune responses, few live bacteria are found, little antibody is produced, and, although skin and peripheral nerves are damaged by the inflammatory responses associated with macrophage activation, the disease progresses slowly and the patients typically survive. Local inflammation, lots of granulomas, Th1 cytokines (IL-2, IFNg, TNFb). • Lepromatous leprosy, type 1 responses are deficient and type 2 response is mounted instead with IL-10, IL-5 and IL-4 cytokines. This results in abundant growth of the bacterium in macrophages and gross tissue destruction. Although high levels of antibacterial antibodies are produced, the antibodies are ineffective because they do not reach the intracellular bacteria. IL-4 can actually inhibit the induction of bactericidal activity in macrophages. There are two polar forms, tuberculoid and lepromatous leprosy, but several intermediate forms also exist. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. IMMUNITY TO VIRUSES • Viruses are obligatory intracellular microorganisms that use components of the nucleic acid and protein synthetic machinery of the host to replicate. • Virus enters a cell via a cell-surface receptor. • A virus is more likely to thrive if it does not kill its host, as sustained coexistence in the host favors the survival and spread of the virus. Other viruses have a long latency period before severe illness, during which time the host may pass the virus to others unknowingly, as in the case of HIV. • Innate and adaptive immune responses to viruses are aimed at blocking infection and eliminating infected cells: KINETICS OF IMMUNE RESPONSES TO A VIRUS INFECTION Natural killer cells (NK cells) are an early component of the host response to virus infection. Experiments in mice have shown that IFN-α, IFNβ, and the cytokines TNF-α and IL-12 are produced first, followed by a wave of NK cells, which together control virus replication but do not eliminate the virus. Virus elimination is accomplished when virus-specific CD8 T cells and neutralizing antibodies are produced. Without NK cells, the levels of some viruses are much higher in the early days of the infection, and the infection can be lethal unless treated vigorously with antiviral compounds. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. Adaptive immune response results in the elimination of the pathogen and development of immunological memory. ANTI-VIRAL INNATE RESPONSES • • • As obligate intracellular pathogens, viruses activate intracellular PRRs that sense viral genetic material and induce type I interferon responses, which activate cell intrinsic mechanisms to limit viral replication in both infected and uninfected cells. Class I MHC expression is often shut off in virus-infected cells as an escape mechanism from CTLs. This enables NK cells to kill the infected cells because the absence of MHC I releases NK cells from inhibition. Viruses in circulation induce activation of the alternative or lectin pathway of complement system, which opsonize or directly lyse viruses. Antiviral mechanisms Destroying the host cell NK cell complement Destroying the virus Erdei A, Sármay G, Prechl J: Immunológia • • • ANTI-VIRAL ADAPTIVE RESPONSES CTLs recognize MHC I presented viral peptides (from matrix proteins, nucleoproteins). Full differentiation of CTLs often requires cytokines produced by Th1 cells or costimulators expressed on infected cells (cross-presentation). CTLs kill the virusinfected cells by their granules (perforin, granzymes) or by FasL expression. CTLs also express anti-viral cytokines (IFNα, IFNβ, TNFα). B cell Antibodies produced by B-cells are effective against viruses only during the extracellular stage of the lives of these microbes, i.e. before they infect host cells, or when they are B cell released from infected cells. Neutralizing antibodies bind to viral envelope or capsid antigens and prevent virus attachment and entry into host cells. IgA is important for neutralizing viruses within the respiratory and intestinal tracts. Virus coupled antibodies activate the complement system, promoting phagocytosis and direct lysis of viruses with lipid envelopes. Destroying the host cell Neurtalizing antibody Destroying the virus complement Destroying the virus by opsonization and phagocytosis Erdei A, Sármay G, Prechl J: Immunológia IMMUNITY TO PARASITES • Parasites include single-celled protozoa, complex multi-cellular worms (helminths, Ascaris, Schistosoma, Trichinella, Cestoda), and ectoparasites (e.g., ticks and mites). • Protozoa can be extracellular (Trypanosoma, Trichomonas) or intracellular (Plasmodium, Leishmania, Toxoplazma). • These organisms are well adapted to resist host defenses, so they survive and replicate, leading to recurrent or chronic infections, tissue destruction. Result: chronic inflammation, fibrosis, granuloma, DTH. • Many of these parasites are resistant to phagocytic killing and may even replicate within macrophages. • Epithelial cells that sense molecular patterns common to helminths (chitin) produce thymic stromal lymphopoietin (TSLP), and IL-33 or IL-25, and activate ILC2s. ILC2 stimulates mucus production by goblet cells and mucosal smooth muscle contractions that facilitate worm expulsion. • Adaptive response is Th2 type (IL-4, IL-5), with IgE isotype, which activates mast cells and eosinophils. Result: degranulation, ADCC. Eosinophils attacking a schistosome larva in the presence of serum from an infected patient. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. The immune response to infection with S. mansoni is dominated by Th2-like mediators, with high titers of antischistosome IgE antibodies, localized increases in degranulating mast cells, and an influx of eosinophils. One eosinophil mediator, called major basic protein (MBP), has been found to be particularly toxic to helminths. (ECF eosinophil chemotactic factor; NCF neutrophil chemotactic factor; PAF plateletactivating factor). Punt, Stranford, Jones, Owen: Kuby Immunology IMMUNE EVASION BY EXTRACELLULAR BACTERIA • Changes in the production of glycosidases lead to chemical alterations in surface LPS and other polysaccharides. • Modulation of expressed antigens (pilin), antibodies become ineffective (Neisseria gonorrhoeae). • Release surface antigens in membrane blebs to decoy antibodies away from the microbes. • Secretion of complement degrading factors, blocking opsonization and lysis by complement (Neisseria meningitidis). • Binding the Fc part of antibodies, blocking their effector functions (Protein A from S.aureus). • Expression of capsular polysaccharides blocks opsonization by complement (Streptococcus pneumoniae). • Inhibition of ROS by secretion of catalase and superoxide dismutase (E. coli). • Resistance to antimicrobial peptides (S. aureus). • Superantigens exhaust the immune system, induce apoptosis of activated T cells. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology IMMUNE EVASION BY INTRACELLULAR BACTERIA • Inhibition of fusion of phagosome with lysosome (Mycobacterium tuberculosis, M. leprae, Legionella pneumophila). • Resistance against lysosomal enzymes, inactivation of reactive oxygen and nitrogen species (Mycobacterium leprae). • Hemolysins (listeriolysin O) lyse the phagosome, escape into cytosol (Lysteria monocytogenes). L. monocytogenes enters human body through the gastrointestinal tract after ingestion of contaminated foods such as cheese or vegetables. When epithelial cells internalize this pathogen for phagocytosis, it can escape from the phagosome, multiplies in the cytosol, and spreads directly to adjacent cells. https://microbeonline.com/virulence-factorslisteria-monocytogenes/ IMMUNE EVASION BY VIRUSES The pathway of class I MHC–associated antigen presentation is shown, with examples of viruses that block different steps in this pathway. In addition to interfering with recognition by CD8+ T cells, some viruses produce “decoy” MHC molecules that engage inhibitory receptors of NK cells. CMV, Cytomegalovirus; ER, endoplasmic reticulum; HCV, hepatitis C virus; HIV, human immunodeficiency virus; HSV, Herpes simplex virus; IFN, interferon; IL, interleukin; MHC, major histocompatibility complex; NK cells, natural killer cells; TAP, transporter associated with antigen processing. Abul Abbas, Andrew Lichtman, Shiv Pillai: Cellular and Molecular Immunology ANTIGENIC-DRIFT AND ANTIGENIC-DRIFT Viruses can alter their antigens and are thus no longer targets of immune responses. The two major antigens of the influenza virus are the trimeric viral hemagglutinin (the viral spike protein) and neuraminidase. Neutralizing antibody that mediates protective immunity is directed at hemagglutinin (H). Antigenic drift (left panels) involves the emergence of point mutants with altered binding sites for protective antibodies on the hemagglutinin. The new variants cause only mild disease in previously infected individuals. Antigenic shift (right panels) is a rare event involving the reassortment of the segmented RNA viral genomes of two different influenza viruses, probably in a bird or a pig. These antigen-shifted viruses have large changes in their hemagglutinin, and therefore T cells and antibodies produced in earlier infections are not protective. These shifted strains cause severe infection that spreads widely, causing the influenza pandemics that occur every 10–50 years. Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. IMMUNE EVASION BY PARASITES • Parasites evade protective immunity by reducing their immunogenicity and by inhibiting host immune responses: • Parasites change their surface antigens during their life cycle in vertebrate hosts (Plasmodium). • Continuous antigenic variation due to changes in expression of the genes encoding the major surface antigen (Trypanosoma). • Living inside host cells (Leishmania, Toxoplasma). • Developing cysts that are resistant to immune effectors (Trichinella). • Shedding of antigens (Entamoeba histolytica). • Inhibition of phagosome-lysosome fusion (Toxoplasma gondii). • Antigen masking with binding human proteins (Schistosoma mansoni). • Expressing complement inhibitors (DAF) (Trypanosoma cruzi). SUMMARY OF IMMUNE RESPONSE AGAINST PATHOGENS Types and characteristics of hypersensitivity reactions. Allergic reactions. Dr. Judit Danis danis.judit@med.u-szeged.hu Immunology 10 Hypersensitivity reactions • Role of immunsystem: to protect agains harmful structures • BUT! Overreaction to harmless stimuli causes hypersensitivity reactions → inflammation and degradation of tissues • Hypersensitivity reactions: – After second (recurrent) antigenexposition – Any organ: mostly: skin, lungs – Classification by Gell and Coombs (1963): Type: I-IV Classification of hypersensitivity reactions by Gell and Coombs • Antibody and immuncomplex derived: – I. Immediate type (Allergy/Anaphylaxy) – II. Antibody mediated (against cell surface or extracellular matrix antigens) – III. Immuncomplex mediated (against circulating antigens) • Cell mediated hypersensitivity – IV. T-cell mediated I. Immediate type hypersensitivity- Allergy • Allergia – 1906 von Pirquet • αλλος (allos) = other • εργον (ergon) = work; ~ changed reactivity • Antic documents: – Hyppias (2. Tyrannos of Athens: pollen allergy) – Roman emperor Claudius and his son Britannicus: horsehair allergy • 1819: mention of hay fever (Dr. John Bostock) • 1865: first skin test (Dr. Charles H. Blackley) • Serum mediated disease: Prausnitz és Küstner, 1921 Dr. Küstner Allergic to fish Dr. Prausnitz Not allergic to fish I. Immediate type hypersensitivity- Allergy • Allergia – 1906 von Pirquet • αλλος (allos) = other • εργον (ergon) = work; ~ changed reactivity • Antic documents: – Hyppias (2. Tyrannos of Athens: pollen allergy) – Roman emperor Claudius and his son Britannicus: horsehair allergy • 1819: mention of hay fever (Dr. John Bostock) • 1865: first skin test (Dr. Charles H. Blackley) • Serum mediated disease: Prausnitz és Küstner, 1921 Dr. Küstner Dr. Prausnitz Dr. Küstner’s serum was injected subcutan to Dr. Prausnitz I. Immediate type hypersensitivity- Allergy • Allergia – 1906 von Pirquet • αλλος (allos) = other • εργον (ergon) = work; ~ changed reactivity • Antic documents: – Hyppias (2. Tyrannos of Athens: pollen allergy) – Roman emperor Claudius and his son Britannicus: horsehair allergy • 1819: mention of hay fever (Dr. John Bostock) • 1865: first skin test (Dr. Charles H. Blackley) • Serum mediated disease: Prausnitz és Küstner, 1921 Dr. Küstner Dr. Prausnitz Local allergic reactions to fish extracts at injection site in Dr. Prausnitz I. Immediate type hypersensitivity- Allergy • Multifactorial disease: – Environment – Genetic background – Immunesystem Genetic background FcƐRI beta chain Cytokines: IL-3, IL-4, IL 5, IL-9, IL-13, GMCSF MHCII alleles Allergy Environment Failure of tolerance during childhood Dysregulation of the Immunesystem Activation of Th1 and Th2 subpopulations IgE production Immunodeficiency Increased eosinophil count I. Immediate type hypersensitivity- Allergy • Multifactorial disease: – Environment – Genetic background – Immunesystem • Immediate reaction after repeated exposure to antigene: – 1. allergen exposure: sensitization – 2. allergen exposure: allergic reaction Allergens • • • • Harmless, non-invasive antigens Mostly proteins Often with enzymatic activity Np common structural or biochemical characteristics • Crossallergy: based on structural homology • Allergens cause an IgE response Allergic reaction 1. Allergen exposure: Sensitization • Antigen presenting cells (dendritic cells) present the allergen to Th2 and B-cells • IgE producing plasmacells are differentiated • IgE binds to FcεRI receptors on mast cells 2. Allergen exposure: allergic reaction • Immediate activation of sensitized mastcells by bound IgE • Degranulation → immediate reactions • Formation of novel mediators → late phase reaction Sensitization Stages of an allergic reaction Mastcell activation • By binding allergens on IgEFcεRI receptors • Activation of signalling: – Degranulation – Transcription of cytokines – Expression of co-stimulatory molecules – Formation of lipid mediators Preformed granules Mediators of mastcells Origin Preformed granules Mediator Effect Histamin Smooth muscel contraction (intestines, lungs) Increase vessel permeability Vessel dilatation Increased mucous production Enzymes (chimase, tryptase, serinestarases, cathepsinG, carboxipeptidases, hydrolases) Activation of matrix metalloproteses Tissue damages Immediate reaction Allergen specific IgE activate mastcells (and basophils), leading to their dreganulation. Allergic reactions are caused by the effect of preformed mediators (histamin and enzymes) on target cells. Effect of mastcell activation in different organs Respiratory system Intestines – Increased fluid secretion – Bronchoconstriction – Increased mucous – Increased peristaltic production Vessels – Vesseldilatation – Increased permeability – Diarrhea – Vomiting – Oedema – Increased lymphflow – Increased infiltration of allergens and immunecells into thetissues ↓ ↓ – Bronchoconstriction, bronchospasm – Swelling of mucosal tissues – Sneezing, coughing, tearing Immediate allergic reactions ↓ Mastcell – B-cell interactions • CD40L is expressed on activated mastcells • CD40L-CD40 interaction increases B-cell activation • Increased IgE production Mastcell • IgE binds to mastcells, further increasing Plasmacell mastcell activation and allergic reaction B-cell Mastcell activation • By binding allergens on IgEFcεRI receptors • Activation of signalling: – Degranulation – Transcription of cytokines – Expression of co-stimulatory molecules – Formation of lipid mediators Lipid mediators Mediators of mastcells Origin Preformed granules Lipid mediators formed after activation Mediator Effect Histamin Smooth muscel contraction (intestines, lungs) Increase vessel permeability Vessel dilatation Increased mucous production Enzymes (chimase, tryptase, serinestarases, cathepsinG, carboxipeptidases, hydrolases) Prostaglandin D2 Leukotrienas Platelet activating factor Activation of matrix metalloproteses Tissue damages Vessel dilatation Bronchoconstriction Increased mucous production Incresed veccel permeability Chemotaxtic for leukocytes Mastcell activation • By binding allergens on IgEFcεRI receptors • Activation of signalling: – Degranulation – Transcription of cytokines – Expression of co-stimulatory molecules – Formation of lipid mediators Produced cytokine Mediators of mastcells Origin Preformed granules Lipid mediators formed after activation Cytokines produced after activation Mediator Effect Histamin Smooth muscel contraction (intestines, lungs) Increase vessel permeability Vessel dilatation Increased mucous production Enzymes (chimase, tryptase, serinestarases, cathepsinG, carboxipeptidases, hydrolases) Activation of matrix metalloproteses Tissue damages Prostaglandin D2 Leukotrienas Platelet activating factor Vessel dilatation Bronchoconstriction Increased mucous production Incresed veccel permeability Chemotactic for leukocytes IL-3 Mastcell proliferation TNFα Inflammation IL-4, IL-13 Help to increase IgE production IL-5 Activation of eosinophil granulocytes Late Phase Response (LPR) Late Phase Response (LPR) • 2-4 hours later, can last for several days • Antihistamins are not effective, can be treated by steroids • Derived by a mediators of mastcells formed after activation (lipid mediators and cytokines) • Leukocyte Infiltration: eosinophils, Th2-lymphocytes, neutrophils → further inflammation • Eosinophils: • Activated by allergen-IgE/IgG immoncomplexes • Preformed mediators from granules: tissue damage, inflammation • Newly formed lipid mediators and cytokine → furhter leukocyte infiltration Mediators of eosinophil granulocytes Origin Preformed granules Mediator Major basic protein (MBP) Eosinophil cationic protein (ECP) Enzymes (eosinophil peroxidase, lysosome hydrolase, phospholipase) Effect Tissue damage and rebuilt Toxic to bacteria, parasites and host cells Lipid mediators formed after activation Leukotrienes Bronchoconstriction Increased mucous formation Increased vessel permeability Cytokines produced after activation IL-3, IL-5, GM-CSF, IL-8, IL-10, CCL-5 (RANTES), MIP-1α, eotaxin Promotes further eosinphil activation Chemotactic for leukocytes Allergic reactions (Anaphylaxia) 1. Localised anaphylaxia: – Localised to antigen entry site – Hay fever – Allergic conjuctivitis – Food allergy – Urticaria – Atopic dermatitic Urticaria Images from the archive of the Department of Dermatology and Allergology. Vanillia-induced oral allergic reaction Allergic reactions (Anaphylaxia) 2. Systemic anaphylaxia – – – – Allergen in blood circulation (medication, insect bite) Multiple organs involved Generalise urticaria Shortness of breath (Bronchoconstriction, bronchospasm, increased mucous production, laryngeal oedema) – Diarrhea, stomach aches – Global vasodilatation → circulatory collapse – Fear of death, loss of consciousness • Treatment: Adrenaline (epinephrine) – vasoconstriction, decreased odeme (alpha-1 adreneg receptors) – increased heartrate, increased blood pressure (alpha-2 adrenerg receptors) – bronchodilation, decreased mastcell and basophil activation (beta-2 adrenerg receptors) Allergia tests – Prick test • Intradermal/Intracutan allergy test • Known amount of allergen is intradermally injected • In allergic patient mast cells degranulation causes skinsymptomps (erythema, edema) • Positive control: Histamin • Negative control: saline • Other methods: molecular IgE-test: specific detetion of IgE from serum (e.g. ImmunoCAP, ELISA) Therapeutic Options Patients allergic to one/few allergens: • Omit allergen • Ameliorate symptomps (antihistamin, corticosteroids) • Immuntherapy (desensibilisation/hyposensibilisation): Subcutan/oral exposure to diluted antigen in increasing concentrations→immuntolerance Patients allergic to many allergens: • Ameliorate symptoms (antihistamin, corticosteroids, biologic therapeutics: anti-IgE antibodies) Pseudoallergy (anaphylaktoid reaction) • Symptomps are similar to allergy, but there is no specific IgE activation • Pseudoallergens can induce direct mastcell degranulation without IgE binding → histamin release Allergen Pseudoallergen IgE antibody FcεRI receptor Mastcell • • • • Medications (NSAID, ACE-inhibitors, CT/MR contrastmaterials) Mediator e.g. Preservatives, artificial food-colorants (Na-benzoate, salicilate, histamin sunset yellow) Foods with high histamincontent or inducing histamin release (red wine, seafood, peanut, soda, onion, paprika, spices) Physical influence (cold, heat, light, mechanic influence) Symptomps ALLERGy PSEUDOALLERGy Pseudoallergy (anaphylaktoid reaction) • No sensibilisation: symptomps can occur by first exposure • Symptomps are dose-dependent: – Low amount: tolerated – High amounts: symptomps • Therapy: – Omit pseudoallergen – Antihistamin Allergen Pseudoallergen IgE antibody FcεRI receptor Mastcell Mediator e.g. histamin Symptomps ALLERGy PSEUDOALLERGy The immunesystem is not involved in pseudoallergic reaction. Pseudoallergy is induced by direct mastcell activation by the pseudoallergen, without IgE involvement. Summary I. Immediate type hypersensitivity- Allergy Start of reaction Within minutes Mechanism Allergen activates mastcells through binding to IgE. Crosslinking of FcεRI receptors causes degranulation (histamin, enzymes) and formation of further mediators. Example Localised anaphylaxia: hay fever, urticaria, food allery Systemic anaphylaxia Classification of hypersensitivity reactions by Gell and Coombs • Antibody and immuncomplex derived: – I. Immediate type (Allergy/Anaphylaxy) – II. Antibody mediated (against cell surface or extracellular matrix antigens) – III. Immuncomplex mediated (against circulating antigens) • Cell mediated hypersensitivity – IV. T-cell mediated II. Antibody mediated (against cell surface or extracellular matrix antigens) • Bound antigens (autoantigens) • IgG and IgM binds to cellsurface antigens or extracellular matrix • Mechanism: – ADCC (IgG) (antibody dependent cell cytotoxicity ADCC Target cell Lysis of target cell – Complementactivation (IgG, IgM) Complement activation →Lysis of target cell • Haemolytic transfusion reaction, hemolytic disease of the newborn, autoimmun diseases II. Antibody mediated (against cell surface antigens) Haemolytic transfusion reaction • • • Blood group incompatibility On RBC of donor: bloodgroup antigens A – A antigen B – B antigen AB – A and B antigens 0 – no antigens Recipient: antibodies against other bloodgroup antigens (IgM, isohemagglutinin): 0 – anti-A and anti-B A – anti-B B – anti-A AB – no antibodies II. Antibody mediated (against cell surface antigens) Haemolytic transfusion reaction Donor: RBC Recipient: antibodies YYYY Modified based on Roumenina et al. Transfusion Medicine Reviews, 2019 II. Antibody mediated (against cell surface antigens) Haemolytic disease of the newborn • Rh- mother, Rh+ foetus: no Rh(D) antigen in the mother 1st pregnancy Placenta Foetal RBC Rh+ Maternal RBC Rh- II. Antibody mediated (against cell surface antigens) Haemolytic disease of the newborn • Rh- mother, Rh+ foetus: no Rh(D) antigen in the mother • 1st pregnancy: Rh(D) antigens on foetal RBC sensitise the mother → maternal anti-Rh(D) antibody production → maternal Rh(D)-specific memory B-cell formation Sensitisation fo the mother Rh(D)-specific Plasmacell Rh(D)-specific B-cell Rh(D)-specific memory B-cells in the mother II. Antibody mediated (against cell surface antigens) Haemolytic disease of the newborn • Rh- mother, Rh+ foetus: no Rh(D) antigen in the mother • 1st pregnancy: Rh(D) antigens on foetal RBC sensitise the mother → maternal anti-Rh(D) antibody production → maternal Rh(D)-specific memory B-cell formation • 2nd pregnancy: anti-Rh(D) antibodies attac the Rh(D)+ RBCs of the foetus • Prophylaxis: mother recieves anti-Rh(D) antibodies after 1st pregnancy, which will bind to the foetal Rh(D)+ RBC, which might get into in maternal circulation to prevent maternal anti-Rh(D) fromation (passive immunisation). Rh(D)-specific Plasmacells Lysis of foetal RBCs Maternal antibodies II. Antibody mediated (against cell surface or extracellular matrix antigens) – Autoimmun diseases • Autoantibodies against self-structures: • 1. extracellular structures → frustrated phagocytosis Goodpasture-syndrome: glomerules in kidney • 2. cellular receptors → inhibition of receptor funcitons Myasthenia gravis: against acetilcholin-receptors • 3. cellular receptors → stimulation of receptor functions Autoimmune hyperthyroidism : against TSH-receptors Normal phagocytosis Opsonisation Recognition by phagocytes Phagocytosis Intracellular degradation • After opsonisation by complement or antibodies, particles will be phagocytosed, killed and degraded intracellularly Frustrated phagocytosis Opsonisation of extracellular surface Recognition by phagocytes Frustrated phagocytosss Degranulation • Opsonisation of extracellular structures • Phagocytosis not possible (too big structures) • Degranulation (enzymes, reactive oxigen and nitrogen species) → Inflammation, tissue degradation Inhibition of receptor functions Myasthenia gravis Normal synapse Myasthenia gravis AchR autoantibodies Nerve ending Anti-acetilcholinreceptor antibodies inhibit the binding of acetilcholin to its receptor, therefore there is no synaptic activation in the disease. Muscle Contraction Inhibition Stimulation of receptor function Autoimmune hyperthyroidism Normal TSH activation in thyroid Autoimmune hyperthyroidism TSHReceptors Thyroid cells Normal thyroid hormone production Excess thyroid hormone production in the absence of TDH Anti-TSH-receptor autoantibodies activate the TSH-receptors, which will induce increased thyroid hormone production even in the absence of TSH. Summary II. Antibody mediated (against cell surface or extracellular matrix antigens) Start of reaction 4-8 hours Mechanism Example Heamolytic transfusion reaction IgG/IgM antibodies against cellular/extracellular matrix structure lead to lysis through complementactivation or ADCC hemolytic disease of the newborn Antibodies against receptors change the metabolism of the cells. Myasthenia gravis Graves-disease, Autoimmune hyperthyroidism Classification of hypersensitivity reactions by Gell and Coombs • Antibody and immuncomplex derived: – I. Immediate type (Allergy/Anaphylaxy) – II. Antibody mediated (against cell surface or extracellular matrix antigens) – III. Immuncomplex mediated (against circulating antigens) • Cell mediated hypersensitivity – IV. T-cell mediated III. Immuncomplex mediated reactions • Circulating antigen • Antibodies and antigens form immuncomplexes: medium-sized immunocomplexes • Medium-sized immuncomplexes are not degraded, rather are deposited in tissues • Deposited immuncomplexes lead to complementactivation • Inflammation, tissue necrosis III. Immuncomplex mediated reactions • Macrophaged are not degrading small and medium-sized immuncomplexes • Immuncomplexes are deposited in circulation: capillary: kidney, joints,plexus choroideus • Complementactivation → vasoactive and chemotactic substances • Neutrophil and macrophage activation → frustrated phagocytosis • Inflammation in the tissue Immuncomplex Antigen Chemotaxis of Neutrophils Antibody Immuncomplex Deposition Platelets Endothel Basalmembran vasoactives Enzymes, Tissue damage III. Immuncomplex mediated reactions Conentration in plasma • Serum disese: – Foreign protein in circulation induces antibody production → immuncomplexes – Antidotes (spider or snake venoms) Foreign proteins usually horse-serum Antibody against foreign protein immuncomplex Symptomps Injection of antidote Time III. Immuncomplex mediated reactions • Serum disese: – Foreign protein in circulation induces antibody production → immuncomplexes – Antidotes (spider or snake venoms) usually horse-serum – Symptoms: fever, rash, joint pain III. Immuncomplex mediated reactions Conentration in plasma • Serum disese: – Foreign protein in circulation induces antibody production → immuncomplexes – Antidotes (spider or snake venoms) Antibody against Foreign proteins foreign protein usually horse-serum – Symptoms: fever, rash, joint pain – Symtopms dissapear after degradation of immuncomplexes immuncomplex – Recurrent antidote treatments: →preformed antibodies →symptomes start faster Symptomps Time →death Injection of antidote III. Immuncomplex mediated reactions • Arthus reaction – Immunizált egyén (IgG) – Lokálisan bejuttatott antigén (szubkután injektálás) – Oltás helyén immunkomplexek alakulnak ki – Immunkomplexek lokálisan lerakódnak, lokális gyulladás alakul ki – Ritkán előfordulhat tetanusz vagy diftéria újraoltás esetén → ezekben az egyénekben még tetanusz profilaxis csak 10 évnél régebbi oltás esetén ajánlott (ACIP – Advisory Committee on Immunization Practices) III. Immuncomplex mediated reactions • Arthus reaction – Immunised individual (IgG) – Local antigen injection (subcutaneous) – Immuncomplex formation at injection site – Local deposition of immuncomplexes lead to local inflammation – Very rare event after Tetanus or Diphteria bosster vaccination: (ACIP – Advisory Committee on Immunization Practices): booster vaccination only if last vaccination was over 10 years ago III. Immuncomplex mediated reactions Autoimmun diseases • Systemic lupus erythematosus (SLE): autoimmun diseases – DNS-anti-DNS immuncomplexes deposition – Acut necrotising vasculitis: in any tissue or organ – Kideny: glomeruolnephritis – Skin: butterfly erythem – Arthritis • Polyartheritis nodosa: – Hepatitis B virus antigen-anti Hepatitis B antitest complexes – Medium sized arteries: (usually kidney) – Inflammation in arteria wall → fibrinoid necrosis Summary III. Immuncomplex mediated reactions Start of reaction 2-8 hours Mechanism Tissue deposition of antigen-antibody complexes (immuncomplexes) activate complement and lead to inflammation and tissue degradation. Example Systemic reakciók: serum disease, glomerulonephritis, SLE, polyartheritis nodosa Local: Arthus-reaction Classification of hypersensitivity reactions by Gell and Coombs • Antibody and immuncomplex derived: – I. Immediate type (Allergy/Anaphylaxy) – II. Antibody mediated (against cell surface or extracellular matrix antigens) – III. Immuncomplex mediated (against circulating antigens) • Cell mediated hypersensitivity – IV. T-cell mediated IV. Cell mediated reactions • • • • „delayed type hypersensitivity” (DTH) : 1-3 days not antibody derived → activated cells: Th1 sensitised Th1 activate macrophages Macrophages eliminate pathogens by their enzymes and cytokines, but also damage the tissue Enzymes, Cytokines Sensitisation Macrophage Tissue damage IFN-γ TNF-α Chemokines activated Macrophage IV. Cell mediated reactions • • • • „delayed type hypersensitivity” (DTH) : 1-3 days not antibody derived → activated cells: Th1 sensitised Th1 activate macrophages Macrophages eliminate pathogens by their enzymes and cytokines, but also damage the tissue • Tuberculin reaction: in case of an active TBC infection, subcutan injected M. tuberculosis extract induces local inflammatory reactions (also in BCG vaccinated patients) • Chronic DTH-reaction: constant presence of pathogen: e.g. granulome formattion (M. tuberculosis, M. leprae) IV. Cell mediated reactions Chronic DTH • Chronic DTH-reaction: constant presence of pathogen (persisting): e.g. granulome formattion (M. tuberculosis, M. leprae) • Antigen presentation activates Th1 cells → cytokine production (IFN-g, TNF-a) • Activation of macrophages and cytotoxic T-cells Activated • Formation of macrophage syncytiums Epitheloid Macrophage cells • Mediators: → tissue damage Macrophage with persisting antigen (APC) →szöveti roncsolás Activated T-cells • Granulome formation T-cell proliferation Syncytium Phagocyted bacteria Degraded bacteria IV. Cell mediated reactions Contact dermatitis • Small antigen (hapten) • Hapten binds to carrier protein (e.g. albumin) • Sensitization (1st exposure) – Hapten-protein complexes are processed by Langerhanscells (LC) – LC migrate to lymphnodes and present hapten to Th-cells – Formation of hapten-specific Th-cells, which migrate to the skin https://link.springer.com/chapter/10.1007/978-3-642-03827-3_3 IV. Cell mediated reactions Contact dermatitis • Elicitation (2nd exposure) – Skin-homing hapten-specific Th-cells are activated by the hapten – IFN-γ from activated Th-cells aktivate keratinocytes and recruit macrophages – Enzymes and reactive oxigen species from macrophages cause tissue damage – Cytokines from keratinocytes and macrophages recruit further cells and cause tissue damage https://link.springer.com/chapter/10.1007/978-3-642-03827-3_3 IV. Cell mediated reactions Contact dermatitis metal • Metals (e.g. nickel) • Organic solvents (e.g. formaldehid, terpentine) • Plant substances (henna) metal button metal earring Images from the archive of the Department of Dermatology and Allergology. watch fabric dye shoe Summary IV. Cell-mediated reaction Start of reaction 1–3 days Mechanism Cytokines from sensitised and activated Th1-cells activate macrophages Cytotoxic T-cells are activeated by cell-bound antigens and lead to tissue damage Example Tuberculin-reaction, granulomes Chronic asthma, cronic allergic rhinitis Contact dermatitis Coeliac disease Thank you for the attention! • Erdei Anna: Immunológia, Medicina Könyvkiadó Zrt, 2012 • Kárpáti Sarolta: Bőrgyógyászat és Venerológia, Medicina Könyvkiadó Zrt, 2013 • A. K. Abbas, A. H. Lichtman, S. Pillai Cellular and Molecular Immunology; Elsevier 7th Edition, 2012 IMMUNSEROLOGIE, IMMUNOLOGISCHE TECHNIKEN I. Immunology 12. Transplantation, immunology of pregnancy, immunodeficiency and it’s pathology. TRANSPLANTATION TRANSPLANTATION GOAL: Replacement of diseased, demaged or worn-out tissues Can be life-saving At the same time may provoke powerful immune responses REQUIREMENTS • Introduce transplants to allow normal functions • Maintain the health of both the recipient and the transplant The immune system of the recipient must be prevented from mounting an adaptive immune respone against the graft to avoid rejection • Inactivation of the immune system The most often „organ transplantation” is the blood transfusion! TRANSPLANTATION DEFINITION Donor: Graft: Host or recipiens: Rejection: Types: person who provide the organ or tissue transplanted organ/tissue or cells person who receives the graft the “functional death” of the organ autolog, allogeneic, xenogeneic graft auto-, allo-, xeno-transplantation THE ALLO-REACTIVE IMMUNE RESPONSE IS DIRECTED AGAINST TRANSPLANTATION ANTIGENS • • • Major transplantation antigens are encoded by classical MHC genes Minor transplantation antigens are encoded by any polymorphic gene and are recognized as peptides in the context of MHC Blood group antigens are considered as tissue-specific transplantation antigens T cells are educated in the presence of self MHC allotypes Other MHC allotypes are recognized as foreign by T-lymphocytes Rejection of incompatible tissue is mediated primarily by T-lymphocytes NK cells and antibody mediated effector functions are also involved TYPES OF TRANSPLANTATION AUTOLOGOUS autograft SYNGENEIC syngraft Skin, muscle, stem cell, dendritic cell, cartilage BLOOD TRANSFUSION Bone marrow-derived haematopoietic cells (HSC) TOLERANCE ALLOGENEIC allograft Kidney, cornea, liver, heart, lung bone marrow-derived haematopoietic cells (HSC) ALLOREACTION TRANSPLANTATION The success of transplantation and survival of the donor tissue depends majorly on histocompatibility GRAFTS WITH MATCHING MHC ARE TOLERATED WHILE ALLOGENEIC GRAFTS ARE REJECTED TRANSPLANT REJECTION Effector phase in the alloreactions: humoral and cellular effector functions Antibody mediated effector functions Mainly type II hypersensitivity reactions (ADCC, frustrated phagocytosis, complement activation à inflammation and the induction of the coagulation cascade) T cell mediated effector functions Type IV hypersensitivity reactions • direct cytotoxicity – CD8+ CTL (MHC class I restriction) • inflammation – CD4+ Th mediated and activated macrophage mediated (MHC class II restriction) GRAFT REJECTION IS THE RESULT OF SPECIFIC IMMUNE RESPONSE Primary rejection mouse strain 10 days Lymfocyte transfer from immunized mouse Rapid rejection of the transplant is mediated by a memory immune response 6 months Secondary rejection mouse strain 3 days - MEMORY Primary rejection mouse strain 10 days MECHANISMS OF TISSUE REJECTION ■ HYPERACUTE REJECTION Ð Ð Xenograft or AB0 incompatible graft Natural IgM antibodies against carbohydrates ■ Ð Antibodies generated upon previous blood transfusion, pregnancy or transplantation – MHC-specific antibodies bind to endothelial cells ■ Ð Ð Ð Galα1-3Gal on xenograft endothelial cells Mismatch of recipient serum with donors B and T cells Complement and clotting system NK cell – mediated IgG-dependent ADCC Necrotic tissue demage ■ EARLY ACUTE REACTION – 2 – 5 days Ð Ð Ð Previous sensitization of cytotoxic T cells IgG-dependent ADCC Necrotic tissue demage ■ LATE ACUTE and CHRONIC REACTION – 7 – 21 days Ð Ð Th1 – mediated cellular immune response Delayed Type Hypersensitivity ■ ■ ■ Ð Fibrosis Proliferation of smooth muscle cells Atherosclerosis Activation of cytotoxic T lymphocytes MECHANISMS OF TISSUE REJECTION AB0 INCOMPATIBILITY Blood transfusion is the most common form of tissue transplantation. Incompatibility of blood group antigens causes type II hypersensitivity reactions. Incompatibility is tested by the cross-match test. The patient’s serum is tested against the red cells of the potential donors. The patient’s red cells are NOT tested against the serum of the donor!!! Organ transplantation requires compatibility of the main blood group antigens HYPERACUTE TRANSPLANT REJECTION IS AN ANTIBODY-MEDIATED TYPE II HYPERSENSITIVITY REACTION • The most dramatic form of tissue incompatibility, begins within minutes to hours • Blood group antigens are expressed by endothelial cells of blood vessels (solid vascularized organs) • antibodies – complement fixation – neutrophil, platelet activation – intravascular coagulation - irreversible ischemic necrosis • CAN NOT BE REVERSED, SHOULD BE AVOIDED!!!!! • Today, hyperacute rejection by anti-abo antibodies is extremely rare. • HLA-I is expressed on vascular endothelium cells, preexisting antibodies (IgG) against HLA class I variants can also cause hyperacute rejection!! HYPERACUTE TRANSPLANT REJECTION SOURCE OF ANTI-HLA ANTIBODY Pregnancy – during childbirth With successive pregnancies, increasing levels of anti-HLA antibodies can develop Blood transfusions (platelets, leukocytes) HLA type is not assessed, the matching being restricted to just the ABO and Rhesus D types Previous organ transplant Cross-match!!! HYPERACUTE TRANSPLANT REJECTION Hyperacute rejection is caused by pre-existing antibodies binding to the graft. ACUTE TRANSPLANT REJECTION Effector phase in the alloreactions: humoral and cellular effector functions Antibody mediated effector functions Mainly type II hypersensitivity reactions (ADCC, frustrated phagocytosis, complement activation à inflammation and the induction of the coagulation cascade) T cell mediated effector functions Type IV hypersensitivity reactions • direct cytotoxicity – CD8+ CTL (MHC class I restriction) • inflammation – CD4+ Th mediated and activated macrophage mediated (MHC class II restriction) IS A T-CELL-MEDIATED TYPE IV HYPERSENSITIVITY REACTION • Acute rejection can be effectively prevented or suppressed by the use of appropriate immunosuppressive therapy • Small subacute rejection events, or subacute inflammations (e.g. in response to small infections) can provide the base conditions for the subsequent chronic rejection events (e.g. the appearance of alloreactive antibodies) ACUTE TRANSPLANT REJECTION BASED ON ALLOANTIGEN RECOGNITION It is essentially the same as the recognition of any foreign (e.g., microbial) protein antigen Lei H, Reinke P, Volk HD, Lv Y, Wu R. Mechanisms of Immune Tolerance in Liver Transplantation-Crosstalk Between Alloreactive T Cells and Liver Cells With Therapeutic Prospects. Front Immunol. 2019 Nov 19;10:2667. doi: 10.3389/fimmu.2019.02667. PMID: 31803188; PMCID: PMC6877506. ACUTE TRANSPLANT REJECTION ACTIVATION OF ALLOREACTIVE T-CELLS Antibodies against graft antigens (most frequently HLA) also contribute to rejection. Antibody production follows the same sequence of events as any helper T-celldependent antibody response (indirect recognition). ACUTE TRANSPLANT REJECTION ACTIVATION OF ALLOREACTIVE T-CELLS Lymphocytes around an arteriole (A) Lymphocytes surrounding the renal tubules (T) Staining of T lymphocytes with anti-CD3 (brown) in the same section The rejected graft is swollen and has deep-red areas of hemorrhage and gray areas of necrotic tissue. CHRONIC TRANSPLANT REJECTION Thickening of the vessel walls and narrowing of their lumens E: endothel G: granulocyte T: alloreactive T M: macrophage EL: elastic lamina SMC: smooth muscle cell Chronic rejection in a kidney allograft with graft arteriosclerosis IS A TYPE III HYPERSENSITIVITY REACTION CHRONIC TRANSPLANT REJECTION HLA MATCHING IMPROVES THE SURVIVAL OF TRANSPLANTED ORGANS (for example kidneys) Blue Orange Red Dark blue Green Black Brown HLA-A, B, C and DR are the most important to match The transplanted organ are often in the state of inflammation: oxygen deprivation, surgical tissue injuries, presence of microbes Inflammation augments the immune reactions. HLA TYPING SEROTYPING MIXED LYMPHOCYTE REACTION by the help of HLA allotype specific antibodies Oldfashioned “classical” method: • Typing „immune sera” Pregnant women are immunised to the HLA allotypes of the newborn during the delivery • Allotype specific monoclonal antibodies Examination • • The response of alloreactive T-cells to foreign MHC molecules can be analyzed in vitro Microcytotoxicity test (complement dependent cytotoxicity, CDC) Flow cytometry DNA-BASED HLA TYPING • PCR-SSOPH: Sequence-specific oligonucleotide probe hybridization • Intermediate resolution, High volume, relatively low cost • Sreening test to identify potential donors or individuals who may later require higher resolution testing • SSP-PCR: Sequence-specific PCR (allele-specific primers) • Rapid (3-4 hours) • Typing of deceased organ donors (speed is important) • SBT: Sequence-based typing • Polymorphic regions are amplified by PCR and then sequenced • The highest resolution HLA typing MINOR HISTOCOMPATIBILITY ANTIGENS The response to minor H antigens is in many ways analogous to that of viral infection Peptides derived from polymorphic cellular proteins bound to MHC class I molecules MEDICAL TREATMENTS IMMUNSUPRESSIVE THERAPY - DEPLETING ANTIBODIES Antibodies that broadly react with white blood cells are given to patients before and after transplantation to deplete these cells and generally weaken the immune system Rabbit antithymocyte globulin (rATG) • Polyclonal mixture of high-affinity antibodies • Binds to T-, B-, NK, dendritic and endothelial cells • Fixes human complement well, delivers the cells to be • killed by phagocytes Alemtuzumab: anti-CD52 • CD52-specific humanized rat monoclonal IgG • CD52 is expressed on almost all lymphocytes, • monocytes and macrophages • Complement fixation, phagocytosis • Alemtuzumab induces a profound, long-lasting lymphopenia MEDICAL TREATMENTS IMMUNSUPRESSIVE THERAPY - CORTICOSTEROIDS VERY EFFECTIVE IMMUNOSUPPRESSIVE DRUGS MEDICAL TREATMENTS IMMUNSUPRESSIVE THERAPY - CORTICOSTEROIDS EFFECTS OF CORTICOSTEROIDS ON THE IMMUNE SYSTEM • Used to treat patients before the transplantation and during episodes of rejection • Many adverse side-effects: fluid retention, weight gain, diabetes, loss of bone mineral, thinning of the skin • Prolonged use is avoided wherever possible • Need novel, milder drugs MEDICAL TREATMENTS IMMUNSUPRESSIVE THERAPY - IMMUNOPHILIN MODIFIERs • Immunophilins are a group of chaperon-like proteins (e.g. cyclophilins, FK506 binding proteins) • Immunophilin modifiers (cyclosporin, tacrolimus, rapamycin) can bind to the immunophilins and modify their function • The formed complexes inhibit the key components of the signal transduction pathways in different cell types (especially in T cells) - calcineurin inhibitors (cyclosporine-cyclophilin complex, tacrolimus-FKBP complex) - mTOR inhibitors (rapamycin-FKBP complex) • Binds to FKBP12, but does not interfere with calcineurin • More toxic than either cyclosporin A or tacrolimus but is a useful component of combination therapy • Does not inhibit the survival and functions of regulatory T-cells MEDICAL TREATMENTS IMMUNSUPRESSIVE THERAPY – INHIBITION OF CO-STIMULATION INHIBITION OF T-CELL CO-STIMULATION BY BELATACEPT, A SOLUBLE FORM OF CTLA-4 BLOCKING CYTOKINE SIGNALING CAN PREVENT ALLOREACTIVE T--CELL ACTIVATION Chimeric basiliximab, humanized daclizumab: monoclonal IgG1 antibodies specific for CD25 Specific for activated T-cells: no wide-ranging effects and immunosuppression associated with many other drugs MEDICAL TREATMENTS INHIBITION OF T-CELL PROLIFERATION Cytotoxic drugs are administered only after transplantation Azathioprine: kidney transplantation • Prodrug, first converted in vivo to 6-mercaptopurine and then to 6-thioinosinic acid • inhibits the production of inosinic acid, an intermediate in the biosynthesis of adenine and guanine nucleotides • No selectivity, collateral damage to those tissues that are always engaged in cell division: bone marrow, intestinal epithelium, hair follicles: anemia, leukopenia, thrombocytopenia, intestinal damage, loss of hair Mycophenolate mofetil: • Metabolized in the liver to mycophenolic acid • Prevents cell division by inhibiting inosine monophosphate dehydrogenase, an enzyme necessary for guanine synthesis Cyclophosphamide: • Originally developed as a chemical weapon (World War I.),aA pro-drug that is metabolized to phosphoramide mustard, a compound that alkylates and cross-links DNA molecules • Specifically damages the bladder, sometimes causing cancer or hemorrhagic cystitis. • Unlike azathioprine, cyclophosphamide is not particularly toxic to the liver, ----- useful alternative for patients with liver damage • Cyclophosphamide is most effective when used in short courses of treatment Methotrexate: • Prevents DNA replication by inhibiting dihydrofolate reductase, an enzyme essential for the cellular synthesis of thymidine. IMMUNSUPRESSIVE THERAPY IMMUNSUPRESSIVE THERAPY The need for HLA matching and immunosuppressive therapy varies with the organ transplanted Corneal transplants: tolerogenic immunological environment 90% success in the absence of HLA matching or immunosuppressive therapy Liver: tolerogenic immunological environment, low HLA1 expression, HLA type is not assessed before transplantation At the other end of the spectrum from eye and liver is the bone marrow HEMATOPOIETIC STEM CELL TRANSPLANTATION • Myeloablative therapy: combination of cytotoxic drugs and irradiation • Engraftment: pluripotent stem cells colonize the bones • When the immune system has been fully reconstituted (can take a year or more), the patient is a chimera (has an immune system which is genetically different) • • • • • HSCs are now obtainable from the blood G-CSF, GM-CSF: stem cells are mobilized from the bone marrow Leukapheresis Isolation: CD34 Between a quarter and half a billion CD34-positive cells are needed to ensure prompt engraftment HEMATOPOIETIC STEM CELL TRANSPLANTATION MORE SHARED HLA ALLOTYPES, MORE ROBUST T-CELL RESPONSE THE SUCCESS OF HSCT CORRELATES WITH THE EXTENT OF THE HLA MATCH BONE MARROW TRANSPLANTATION Special case of tissue transplantation Graft-donor T •Graft versus host reaction GVH •Graft versus host disease – GVHD •chronic and systemic Recipient peptide Recipient APC survive Recipient peptide Graft-donor T Graft Versus Host Reaction • Mature T cells transplanted with the bone marrow react with recipient cells • Elimination of donor T cells can prevent GVHD •Elimination of donor T cells decreases graft versus leukemia effect •Bone marrow transplantation is used for correcting SCID GRAFT VERSUS HOST DISEASE (GVHD) GRAFT-VERSUS-HOST DISEASE: ALLOREACTIVE DONOR TCELLS IN THE GRAFT ATTACK THE RECIPIENT’S TISSUES The conditioning regimen creates cytokine storm A systemic type IV hypersensitivity reaction that can prove fatal GRAFT VERSUS HOST DISEASE (GVHD) GRAFT-VERSUS-HOST DISEASE: ALLOREACTIVE DONOR T-CELLS IN THE GRAFT ATTACK THE RECIPIENT’S TISSUES Prevention: T-cell depletion Treatment: Methotrexate in combination with cyclosporin A Markedly reduced GVHD: higher incidence of graft failure A systemic type IV hypersensitivity reaction that can prove fatal GRAFT VERSUS HOST DISEASE (GVHD) THE PROBABILITY OF GVHD CORRELATES STRONGLY WITH THE EXTENT OF HLA MISMATCH Minor histocompatibility antigens trigger alloreactive T-cells in recipients of HLA-identical transplants (red) ) GRAFT VERSUS HOST DISEASE (GVHD) TRANSPLANT REJECTION VS GVHD GRAFT VERSUS HOST DISEASE (GVHD) The rash characteristic of GVHD often starts on the face. Panel a: early GVHD in the skin. Lymphocytes are emerging from blood vessels (lower arrow) and adhering to the basal layer of the epidermis (upper arrow). Panel b: the basal cells of the epidermis begin to swell and vacuolate. GRAFT-VERSUS-LEUKEMIA (GVL) EFFECT • • Alloreactive T-cells in the graft help rid the patient of residual leukemia cells Promotion of GVL reaction, less emphasis on tumor elimination by chemotherapy and irradiation • Less severe conditioning regimens: hematopoietic system is damaged but not destroyed, quicker recovery One approach: transfusions of donor T- cells at a time after transplantation when the inflammation caused by the conditioning regimen has subsided and the likelihood of GVHD is diminished • Reconstitution of NK cells occurs more rapidly than that of T-cells Alloreactive NK cells can emerge B.M. Triplett, E.M. Horwitz, R. Iyengar et al., Leukemia 23:1278–1287, 2009. IMMUNOLOGY OF PREGNANCY A unique problem Pregnancy is an immunologically very complex problem for the mother. An essential element in the defense of the immune system is the elimination of foreign matter to the body. In contrast, a pregnant mother feeds a fetus that is antigenically foreign to itself for many weeks or months. Accordingly, cells and molecules in the maternal immune system must interact to prevent the rejection of the semiallogene fetus and to support its growth and development. The exact mechanisms are still unknown to this day, however, understanding how the maternal immune system responds to pregnancy is critical to better diagnosing, understanding, and treating various pregnancy complications. THE MATERNAL-FETAL INTERFACE Anatomy of the maternal–fetal interface. The fetus is entirely surrounded and encased by placental and chorion membrane trophoblast cells. Maternal cells and fetal cells are intermixed in the decidua basalis, the site of attachment of the placenta to the uterus (upper insert) and between the chorion membrane and decidua parietalis (left insert). CTB, cytotrophoblast cells; sTB, syncytiotrophoblast. Source: Reprinted from Placenta 32 (Supplement B, Trophoblast Research vol. 25), M. Petroff: Fetal antigens: identity, origins and influences on the maternal immune system, S176S181, Copyright 2011, with permission from Elsevier. Made by Biorender IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE The placenta is essentially the maternal-fetal interface serving as an anatomical barrier between baby and mother (with separate circulatory systems). Despite this, the placenta is abundant with immune cells and mediators, including Uterine Natural Killer cells (70%), macrophages (20%), T cells (including CD4+, CD8+, g/d T cells, regulatory T cells) (10%), dendritic cells and B cells (few). The numbers of these cells and roles that they play differs throughout the various stages of pregnancy. LEUKOCYTE CELL LINEAGES WITH KEY ROLES IN THE MATERNAL IMMUNE RESPONSE TO PREGNANCY Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE Mor, G., Aldo, P. & Alvero, A. The unique immunological and microbial aspects of pregnancy. Nat Rev Immunol 17, 469–482 (2017). https://doi.org/10.1038/nri.2017.64 IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE IMMUNE CELLS AT THE MATERNAL-FETAL INTERFACE The presence of immunocytes in the decidua is prerequisite of a successful pregnancy. Immunocytes are present in the decidua to promote implantation, rather then attack the embryo MULTIPLE MECHANISMS UNDERLIE MATERNAL TOLERANCE OF THE FETUS Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 MATERNAL–FETAL CELL COEXISTENCE AND EXCHANGE Source: Reprinted from Placenta 32 (Supplement B, Trophoblast Research vol. 25), M. Petroff: Fetal antigens: identity, origins and influences on the maternal immune system, S176S181, Copyright 2011, with permission from Elsevier. Made by Biorender INDUCTION OF IMMUNE TOLERANCE DC and T cell responses that occur during pregnancy better parallel what is observed during the induction of immune tolerance than during the process of T cell activation in the context of organ transplant rejection. Mor, G., Aldo, P. & Alvero, A. The unique immunological and microbial aspects of pregnancy. Nat Rev Immunol 17, 469–482 (2017). https://doi.org/10.1038/nri.2017.64 INDUCTION OF IMMUNE TOLERANCE IMPLANTATION OF THE BLASTOCYST AND FORMATION OF METASTASES ARE SIMILAR PROCESSES. The attachment of a micrometastatic tumour to a new tissue site has been shown to initiate a pro-inflammatory process that is characterized by the presence of angiogenic factors, growth and survival factors, and cytokines and chemokines that are necessary for the establishment and growth of the metastasizing tumour Once established in the tissue, the tumour cells are able to modify the tissue microenvironment towards a T helper 2 (TH2)-type or anti-inflammatory milieu, which can increase the recruitment of ‘M2-like’ macrophages, myeloid-derived suppressor cells (MDSCs) and regulatory T (Treg) cells. This change in the immune landscape sustains the tumour and promotes its growth. Mor, G., Aldo, P. & Alvero, A. The unique immunological and microbial aspects of pregnancy. Nat Rev Immunol 17, 469–482 (2017). https://doi.org/10.1038/nri.2017.64 THREE DISTINCT IMMUNOLOGICAL STAGES OF FETAL DEVELOPMENT Immune states at different stages of embrionic development: 1. Pro-inflammatory stage that is associated with implantation and placentation; 2. Anti-inflammatory stage, concommittant with fetal growth; 3. Second pro-inflammatory stage that is responsible for the initiation of parturitio PRO-INFLAMMATORY STAGE Förger, F., Villiger, P.M. Immunological adaptations in pregnancy that modulate rheumatoid arthritis disease activity. Nat Rev Rheumatol 16, 113–122 (2020). https://doi.org/10.1038/s41584-019-0351-2 PRO-INFLAMMATORY STAGE • • Vascularization Development of decidua PRO-INFLAMMATORY STAGE No DC • • No NK cell Mor, G., Aldo, P. & Alvero, A. The unique immunological and microbial aspects of pregnancy. Nat Rev Immunol 17, 469–482 (2017). https://doi.org/10.1038/nri.2017.64 Vascularization Trophoblast PRO-INFLAMMATORY STAGE The function of dendritic cells (DC) in implantation Decidual DC do not migrate into lymph nodes (resident) → tolerance Factors secreted by DCs remove the mucin layer of the surface epithelium of the uterus, exposing adhesion molecules that will facilitate the attachment of the embryo. Further inflammatory signals originating in the uterine stroma guide the invasion of the trophoblast into the wall of the endometrium to promote successful implantation. PRO-INFLAMMATORY STAGE Uterine NK cells cooperate with fetal extravillous trophoblast cells to provide the placenta with an adequate supply of maternal blood. Cooperation between extravillous trophoblast cells and uterine NK cells is controlled by fetal HLA class I Peter Param_The Immune System 4th edition_2015 ANTI-INFLAMMATORY STAGE ANTI-INFLAMMATORY STAGE Förger, F., Villiger, P.M. Immunological adaptations in pregnancy that modulate rheumatoid arthritis disease activity. Nat Rev Rheumatol 16, 113–122 (2020). https://doi.org/10.1038/s41584-019-0351-2 ANTI-INFLAMMATORY STAGE ANTI-INFLAMMATORY STAGE Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 ANTI-INFLAMMATORY STAGE Immune-modulation by HLA-G Žs HLA-E EVT: extravillous trophoblast CT: cytotrophoblast ST: syncytiotrophoblast Dahl et al. Human Reproduction Update, Vol.18, No.1 pp. 92Ð109, 2012 ANTI-INFLAMMATORY STAGE Mechanisms of immune tolerance (I) Lack of polymorphic HLA molecules on trophoblasts HLA-G isoforms and their receptors ANTI-INFLAMMATORY STAGE Trophoblast-mediated immune regulation ANTI-INFLAMMATORY STAGE Trophoblast-mediated immune regulation Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 ANTI-INFLAMMATORY STAGE T-Reg cells Suppressive pathways of Treg cells. Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 IMMUNOLOGICAL BALANCE AT THE FETO-MATERNAL INTERFACE DURING EARLY PREGNANCY Saito etal, i: 10.3389/fimmu.2019.00573 EVIDENCE FOR SHIFTED TH1/TH2 BALANCE DURING PREGNANCY Sarah A. Robertson and Margaret G. Petroff: Immunology of Pregnancy, Chapter · December 2015, DOI: 10.1016/B978-0-12-397175-3.00041-7 HIGH PROGESTERON LEVEL IS MAINTAINED THROUGHOUT PREGNANCY PROGESTERONE-INDUCED BLOCKING FACTOR (PIBF • Its serum concentration gradually increases between weeks 7-37 of pregnancy • augments production of Th2-cytokines • controls (inhibits) activity of NK cells • Inhibits release of arachidonic acid • Decreases prostaglandin production • Decreased serum levels are associated with premature birth SECOND PRO-INFLAMMATORY STAGE Förger, F., Villiger, P.M. Immunological adaptations in pregnancy that modulate rheumatoid arthritis disease activity. Nat Rev Rheumatol 16, 113–122 (2020). https://doi.org/10.1038/s41584-019-0351-2 SECOND PRO-INFLAMMATORY STAGE Myometrium: • massive influx of inflammatory cells (neutrophils and macrophages) into both the lower and the upper segment of myometrium • Leukocytic influx is paralleled by up-regulation of proinflammatory cytokine mRNA expression, specifically IL-1β, IL-6 and IL-8. Cervix: • labour is associated with a massive influx of leukocytes into the cervix • Each of the three nitric oxide synthase enzymes is produced in the cervix • NO-donors are considered as alternative of prostaglandins to facilitate cervical ripening Fetal membranes: • No increase in leukocyte cell numbers • BUT, fetal membranes have an acute inflammatory signature Clinical & Translational Immunology, Volume: 9, Issue: 4, First published: 14 April 2020, DOI: (10.1002/cti2.1121) SECOND PRO-INFLAMMATORY STAGE Mendelson CR, Montalbano AP, Gao L. Fetal-to-maternal signaling in the timing of birth. J Steroid Biochem Mol Biol. 2017 Jun;170:19-27. doi: 10.1016/j.jsbmb.2016.09.006 SUMMARY Several local and systemic modifications are now suggested to be involved in protection of the developing fetus from attack by the maternal immune system, mainly: ➢ Cytokine shift Successful pregnancy is associated with a dominance of Th2-type immunity, and induction of Th1-type responses considered potentially dangerous for the continuation of pregnancy. This paradigm has been expanded to consider Tregs and Th17 cells, with Tregs playing pregnancy-protective roles and Th17 responses being detrimental to pregnancy. ➢ Influence of female sex hormones Estrogen and progesterone levels are massively upregulated during pregnancy, and both hormones have been shown to have immunomodulatory functions, impacting immune cell recruitment, expansion and function. ➢ Unique HLA expression by trophoblasts Trophoblasts are the main cell type of the placenta, and exhibit unique Major Histocompatibility Complex (MHC) expression compared to mother and baby. MHC class II molecules are not expressed by trophoblasts. HLA-C, E, F, and G (of the MHC class I type) are expressed by trophoblasts and have functions IMMUNDEFICIENCIES ■ INHERITED (PRIMARY) ■ ACQUIRED Ð Loss of function mutation of genes of the immune system Ð Ð Ð Ð Ð Ð Enhanced susceptibility to infections Ð Particular types of pathogens depending on the gene defect Ð Did not show up until 1950 antibiotics Due to infectious diseases AIDS Other virus infections Malnutrition Artificial immunosuppression Ð Ð Drugs Radioactive irradiation IMMUNDEFICIENCIES ■ PRIMARY IMMUNODEFICIENCIES MAY CAUSE SUSCEPTIBILITY TO A WIDE RANGE, A SMALL SET OF PATHOGENS OR EVEN TO A SINGLE TYPE OF PATHOGEN Ð Susceptibility to multiple type of organisms Ð Immunodeficiencies with lack of functional T-cells (severe combined immunodeficiency) Ð Immunodeficiencies with lack of functional B-cells (Immunoglobulin deficienciews) Ð Many deficiencies affecting innate cell functions Ð Many complement deficiencies Ð Susceptibility to a small set or to a specific organism. Ð IL12/IL12R IFNϓ-receptor deficiencies (mycobacteria) Ð AIRE deficiency (candida) Ð Complement C5-C9 (MAC a Neisseria sp) ■ MOST ARE RECESSIVE MUTATION OF SINGLE GENES Autosomal genes 1. Recessive traits Ð Disease in homozygous children Ð Heterozygous children are carriers Dominant traits have been eliminated from the population Ð IFNγ receptor – dominant/recessive X-linked genes Ð Single gene defect causes disease in males Ð Single gene defect in females renders the affected woman carrier DISSEMINATED MYCOBACTERIAL INFECTION (BCG) THE IMPACT OF RECESSIVE AND DOMINANT MUTATIONS IN THE IFN-γ RECEPTOR ON MONOCYTE ACTIVATION DISSEMINATED MYCOBACTERIAL INFECTION (BCG) IL-12 RECEPTOR DEFICIENCY PRODUCES A SIMILAR SUSCEPTIBILITY TO INTRACELLULAR BACTERIAL INFECTIONS NUMEROUS IMMUNODEFICIENCY LOCI RESIDE ON THE X CHROMOSOME CGD: Chronic Granulomatous Disease WAS: Wiscott-Aldrich Syndrome SCID: Severe Combined Immunodeficiency XLA: X-linked Agammaglobulinemia XLP: X-linked Lymphoproliferative Disease XLHM: X-linked Hyper-IgM Syndrome TYPES OF INHERITED IMMUNODEFICIENCIES INNATE IMMUNITY • • PHAGOCYTIC SYSTEM Enhanced susceptibility to bacterial infections • • • • • LAD1: CD18 (CR3, CR4, LFA1) NADPH oxidase G6PD Myeloperoxidase CHS1/LYST • • • • • • • • • COMPLEMENT SYSTEM Some infections, primarily with encapsulated organisms and Neisseriae Immunocomplex deposition Soluble and membrane factors C1 – C4 Alternative pathway C3 Terminal components Complement inhibitors TYPES OF INHERITED IMMUNODEFICIENCIES ADAPTIVE IMMUNITY • ANTIBODY DEFICIENCY • Recurrent sinopulmonary and GI infections beginning after 3-4 mo. B-cell development/activation RAG-1, RAG-2 Artemis DNA-PK ADA XLA IgA deficiency Hyper IgM syndrome B-/T-cell collaborations CD40 ligand, XLHIM • • • • • • • • • • • • T-CELL DEFICIENCY SCID: opportunistic infections manifest early in infancy • • • • • • • T-cell development IL-7/Jak3 RAG-1 RAG-2 Artemis DNA-PK ADA BLS DEFECTS IN PHAGOCYTE FUNCTION ENHANCED SUSCEPTIBILITY TO BACTERIAL INFECTIONS LEUKOCYTE ADHESION DEFICIENCY (LAD1) Ø CD18 DEFICIENCY (ITGB2;21q22.3Common β-subunit of CR3, CR4 and LFA-1 Ø Blocked phagocyte migration from blood to the site of infection Ø Inhibited uptake and degradation of opsonized bacteria DEFECTS IN PHAGOCYTE FUNCTION ENHANCED SUSCEPTIBILITY TO BACTERIAL INFECTIONS LEUKOCYTE ADHESION DEFICIENCY (LAD1) Ø Common β-subunit of CR3, CR4 and LFA-1 Ø Blocked phagocyte migration from blood to the site of infection Ø Inhibited uptake and degradation of opsonized bacteria Ø Persistant infection with extracellular bacteria, pyogenic infections (No opportunistic infections) Ø Defect in wound healing, omphalitis, pneumonia, gingivitis, peritonitis Ø Lethal within the first decade of life without bone marrow transplantation Gingivitis Omphalitis Non-healing wound DEFECTS IN PHAGOCYTE FUNCTION CHRONIC GRANULOMATOUS DISEASE – CGD Mutation of NADPH oxidase – any of the 4 subunits (most common: gp91 – X-linked) • No superoxid O2- radical è antibacterial activity is compromised • Chronic intracellular bacterial or fungal infections – granuloma formation • Aspergillus pneumonia, suppurative arthritis, osteomyelitis, superficial skin infections (cellulitis, impetigo) DEFECTS IN PHAGOCYTE FUNCTION Ø Glucose-6-phosphate dehydrogenase linked) • Less severe phenotype • Reduced NADPH level • Predisposes to hemolysis • Selective advantage - malaria deficiency (X- Ø Myeloperoxidase deficiency (Chr 17) • Less severe phenotype • Myeloperoxidase produces cytotoxic hypochlorous acid (HOCl) from hydrogen peroxide (H2O2) and chloride anion (Cl−) • Respiratory burst with a normal nitro blue tetrazolium (NBT) test • Disseminated candidiasis DEFECTS IN PHAGOCYTE FUNCTION CHÉDIAK-HIGASHI SYNDROME Neutrophil Lysosomal trafficking regulator deficency CHS1/LYST (1q42) Ø Abnormal intracellular protein transport Ø Failure of phagolysosome formation, phagocytosed material is not delivered to lysosomes Eosinophil Ø Abnormally giant granules in white blood cells Ø Severe immunodeficiency, NK cell, CTL defect, neutropenia Ø Persistent and recurrent bacterial infections Ø Infections most commonly involve the skin, the lungs, and the respiratory tract and are usually due to Staphylococcus aureus, Streptococcus pyogenes, and Pneumococcus species. Ø Accelerated phase (85%): fatal in early childhood, lymphoproliferation, hepatosplenomegaly Ø Defective melanization - Oculocutaneous albinism: hypopigmentation: skin, hair, eyes, photophobia COMPLEMENT DEFICIENCIES CLASSICAL PATHWAY ALTERNATIVE PATHWAY EARLY COMPONENTS INFECTIONS EARLY COMPONENTS Factor B: No case described Factor D: Rare, increased risk of infections Inadequate humoral response Decreased production of the opsonin C3b Sinopulmonary infections Streptococcus pneumoniae Haemophilus influenzae Neisseria meningitidis AUTOIMMUNITY Accumulation of immune complexes Tissue demage Inflammation SLE, RA C C3 5 C 6 C 7 C 8 C 9 Properdin: The only X-linked complement protein Increased susceptibility to bacterial infections of the Neisseria family (fulminant meningococcal disease) TERMINAL COMPONENTS Invasive meningococcal disease Disseminated gonococcal infection COMPLEMENT DEFICIENCIES C3: CENTRAL POSITION Defective synthesis, expression or secretion of C3: AUTOIMMUNE/INFECTIONS OR BOTH Autoimmune disorders: SLE-like, glomerulonephritis Secondary C3 deficiency: Impairment in the regulatory proteins factor I or factor H C3 C 5 C 6 C 7 C 8 C 9 Recurrent, severe, invasive infections Gram+/GramS. pneumoniae, S. pyogenes, S. aureus N. meningitidis, H. influenzae Impaired responses to immunization COMPLEMENT INHIBITOR DEFICIENCIES DEFICIENCIES OF C3 CONVERTASE INHIBITORS Factor I: Cleavage of C4b, C3b Factor H: C3bBb inhibitor Co-factor of factor I Uncontrolled amplification of C3 cleavage results in acquired C3-deficiency Higher susceptibility to S. pneumoniae and N. meningitidis infections Immune complex deposition-mediated diseases (SLE, glomerulonephritis) aHUS: atypic hemolytic uremic syndrome: systemic thrombotic microangiopathy, stroke, heart attack, renal failure, and death Mutations in factor H and factor I are associated with aHUS Mutation of membrane co-factor protein CD46 (MCP) is also associated with aHUS COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) Acquired clonal mutation of pig-a gene (X-chromosome) in myeloid progenitors No GPI-anchored proteins in the cell membrane of affected cells (rbc, plt, wbc) PIG-A = Phosphatidylinositol Nacetylglucosaminyltransferase subunit A A CD55 (DAF) és CD59 (MIRL) complement regulatory proteins are GPI-anchored proteins COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) Normal, CD55/DAF+ and CD59/MIRL+ red blood cells can resist complementmediated lysis Doi:10.3324/haematol.2009.017848 COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) Absence of CD55/CD59 leads to MAC-mediated intravascular hemolysis Doi:10.3324/haematol.2009.017848 COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) INTRAVASCULAR HEMOLYSIS Release of hemoglobin Release of erythrocyte arginase Large amounts of Hb deplete haptoglobin Conversion of L-arginine, the substrate for NO synthesis, to ornithine Free Hb irreversibly binds to nitric oxide (NO) NO SCAVENGING PLATELET AGGREGATION THROMBOSIS COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) Magnetic resonance angiography in a patient with PNH and superior sagittal sinus thrombosis with collateral vessel formation Anita Hill et al. Blood 2013;121:4985-4996 Case of dermal vein thromboses in a patient known to have PNH COMPLEMENT INHIBITOR DEFICIENCIES PAROXYSMAL NOCTURNAL HEMOGLOBINURIA (PNH) COLOUR OF URINE SAMPLES TAKEN FROM PNH PATIENT AT DIFFERENT TIMES B-CELL IMMUNDEFICIENCIES SYMPTOMS OF B-CELL DEFICIENCIES MANIFEST REALTIVELY LATE DUE TO THE PRESENCE OF MATERNAL ANTIBODIES Approx. 70% of all IDs. Increased sensitivity to: Encapsulated bacteria, Streptococcus pneumoniae, Haemophylus influenzae, Enteroviruses, parasites B-CELL IMMUNDEFICIENCIES ANTIBODY DEFICIENCY X-LINKED AGAMMAGLOBULINEMIA, XLA Genetic defect: • Mutation in the Bruton’s tyrosine kinase, essential for B-cell activation and development • NO B-CELLS IN THE PERIPHERY – block at pre B-cell stage • Male XY HEALTHY – XY DISEASE • Carrier female XX HEALTHY – non-random inactivation of X in B-cells • INABILITY TO CLEAR EXTRACELLULAR BACTERIA • (Bruton’s agammablobulinemia), 1:200,000 B-CELL IMMUNDEFICIENCIES ANTIBODY DEFICIENCY X-LINKED AGAMMAGLOBULINEMIA, XLA Normal XLA Symptoms: First few months of life is relatively normal (maternal Ig) Ð Tonsils are small, lymph nodes are barely palpable Ð Increased susceptibility to bacteria and enteroviruses (likely due to IgA defficiency) Encapsulated bacteria resisting ingestion by phagocytes unless they are coated with antibody and complement Ð Ð Recurrent infection of sinuses and of the middle ear, pneumonia Ð Pyogenic bacteria – permanent tissue demage caused by enzyme release from bacteria and phagocytes – bronchiectasis, chronic lung disease ■ Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus Oral polio vaccine disseminates and causes poliomyelitis Ð T-cell responses to intracellular bacteria is normal (mycobacteria) Ð Treatment: Monthly injections of Gamma globulin (IVIG or SC) Ð B-CELL IMMUNDEFICIENCIES ANTIBODY DEFICIENCY NON BRUTON’S AGAMMAGLOBULINEMIA X-LINKED HYPER IgM SYNDROME (XLHIM) DIMINISHED ANTIBODY PRODUCTION AS A RESULT OF INHERITED DEFECT OF T-CELL HELP AUTOSOMAL Ø µ heavy chain (IGHM) Ø λ5 (IGLL1) Ø lgα (CD79A) Ø lgß (CD79B) Genetic defect: Ð Ð Ð Defect of the CD40L gene (Xq26) Symptoms: No specific antibody response to T-dependent antigens ■ low IgG, IgA, IgE No macrophage/B-cell/DC activation by T-cells – CD40 – CD40L LACK OF GERMINAL CENTERS IN LYMPH NODES OF X-LINKED HYPER-IGM SYNDROME PATIENTS B-CELL IMMUNDEFICIENCIES SELECTIVE IgA DEFICIENCY IgA: protection against infections of the mucous membranes Ø Occurance: 1:160-1:800 (Europe, less in Asia) Ø May be asymptomatic, but often associated with chronic or recurrent disease of the respiratory system Ø Giardia infection with chronic diarrhea is frequent Ø Higher frequency of allergies Ø Tenfold risk of coeliac disease Ø Autoimmune disease, autoimmune cytopenia Ø 40% of patients develop anti-IgA antibodies (transfusion, anaphylaxis) Chest radiograph of a 50-year-old man with immunoglobulin A deficiency and severe bilateral pneumonia T-CELL IMMUNDEFICIENCIES SEVERE COMBINED IMMUNODEFICIENCY,SCID DEFECT IN T-CELL FUNCTIONS T-cells are involved in all aspects of adaptive immunity ■ Neither T-cell-dependent antibody response nor cellular immunity are functional ■ Persistent and recurrent infections with a broader range of pathogens than patients with B-cell deficiences T-CELL IMMUNDEFICIENCIES SEVERE COMBINED IMMUNODEFICIENCY,SCID • • • Mutation of RAG enzymes – T-B-NK+ Mutation of DNA-PK/Artemis – T- B-NK+ Omenn syndrome – T+B-/low, hypomorphic mutation of RAG1/2 (or Artemis) – T-cell counts are normal to elevated – Restricted TCR repertoire – Activated Th2 phenotype – Eosinophilia, elevated IgE level – Recurrent infections, mainly opportunistic – Autoimmunity: T-cell infiltration: GI tract, skin, hepatosplenomegaly, lymphadenopathy – Exfoliative dermatitis (erythroderma) – Failure to thrive, RAPIDLY FATAL T-CELL IMMUNDEFICIENCIES SEVERE COMBINED IMMUNODEFICIENCY,SCID TREATMENT • • • • • Gene therapy Bone marrow transplantation (BMT), preferably from a histocompatible sibling Often SCID babies need to be stabilized first before BM-transplant as they have severe infections when brought to the clinic Survival of HEALTHY SCID babies after BMT is over 95%! Testing before diseases develops??? EARLY DIAGNOSIS CAN SAVE MANY LIVES !!!! WISKOTT-ALDRICH SYNDROME (WAS) A disease of defective re-organization of the actin cytoskeleton Genetic defect: Ð Mutation in the WAS protein (WASP) expressed in white blood cells and megakaryocytes, Xlinked Symtomps: Ð Thrombocytopenia, small platelet size (decreased production of platelets in bone increased destruction in spleen) marrow, WISKOTT-ALDRICH SYNDROME (WAS) A disease of defective reorganization of the actin cytoskeleton Genetic defect: – Mutation in the WAS protein (WASP) expressed in white blood cells and megakaryocytes, X-linked Symtomps: – Thrombocytopenia, small platelet size (decreased production of platelets in bone marrow, increased destruction in spleen) – Rearrangement of cytoskeleton upon T-cell activation in the polarized contact with B-cells, macrophages and target cells is defective. – – Normal lymphocyte surface is covered with abundant microvilli, which are sparse or absent from the patient's lymphocytes. The marginal zone which contains B lymphocytes and specialized macrophages is severely reduced in size. Low IgM high IgA, IgE serum levels – – Eczema. B-cell lymphomas – – Pyogenic and opportunistic bacterial infections Severe infection with varichella (chicken pox) and herpes simplex (impaired CD8+ Tcell response) – Treatment: Bone marrow transplantation

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