University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2021
Views:

57

Pages:

71
Author:

imophulebf12

Overview of the Immune System Objectives Purpose of the immune system Cellular basis of immunity Induction of response Effectors of response Ontogeny Functions of the Immune System Protection against foreign invaders into body Produce / protect germ free environment of the body Foreign Invaders Protection Against Foreign Invaders Into Body Foreign Invaders Into Body Why do surgeons use gloves for surgery if your hands have been washed? Produce / Protect Germ Free Environment 32583 19761 Produce / Protect Germ Free Environment Three Key Steps of Combating Infections reak the cycle of transmission ill the infectious agent ncrease host resistance e.g., increase immunity of host Lines of Defense First Line: Physical Barrier – Skin: Stratum Cornium – HCl In Stomach – Mucus In Intestines reak the cycle of transmission Lines of Defense Second line: Phagocytes at work Neutrophils to ill the infectious agent Monocytes - macrophage CT Mononuclear phagocyte system - Group of phagocytotic cells that are monocyte (from bone marrow) derived and carried in blood that take up residence in various organs throughout the body. Monocyte in blood lung liver Lines of Defense Phagocytes at work – Neutrophils – Macrophages Two types of immunity: Innate immunity vs adaptive immunity Innate immunity refers to nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. Adaptive immunity refers to specific defense mechanisms which are acquired and have specificity and memory. ncrease host resistance through Immunity Characteristics of Adaptive Immunity Acquired - requires exposure to antigens Specificity - response is unique to exposure Memory - remembers previous exposure (basis of immunization) Characteristics of Immunity Innate immunity protects the new born before adaptive immunity has developed Adaptive immunity must be acquired – developed Colostrum Colostrum Colostrum is known to contain immune cells (as lymphocytes)[4] and many antibodies such as IgA, IgG, and IgM. These are the major components of the adaptive immune system. Inter alia IgA is absorbed through the intestinal epithelium, travels through the blood, and is secreted onto other Type 1 mucosal surfaces. Other immune components of colostrum include the major components of the innate immune system, such as lactoferrin,[5] lysozyme,[6] lactoperoxidase,[7] complement,[8] and proline-rich polypeptides (PRP).[9] A number of cytokines (small messenger peptides that control the functioning of the immune system) are found in colostrum as well,[10] including interleukins,[10] tumor necrosis factor,[11] chemokines,[12] and others. http://en.wikipedia.org/wiki/Colostrum Characteristics of Immunity Acquired Must be developed Specificity Antibodies made are specific to specific molecules on the antigen of exposure Characteristics of Adaptive Immunity Memory: quick second response – Long lived cells Acquired Specificity Memory Primary and secondary response of B lymphocytes for differentiation of plasma cells that produce antibodies Types of Immune Response Antibody: mediated – Glycoproteins recognize and bind to antigens Cell: mediated – Specifically active cells recognize cell - bind antigens EXAMPLES OF IMMUNE RESPONSE REACTION AGAINST MICROORGANISMS: BACTERIA, VIRUSES, PARASITES REACTION AGAINST TUMOR CELLS ALLERGIC REACTIONS: HAY FEVER, POISON IVY AUTOIMMUNE REACTION: ARTHRITIS, TYPE I DIABETES GRAFT REJECTION http://www.greenlifestyle.be Appendix Organs of the Immune System Primary organs – Bone marrow – Thymus Secondary organs – Spleen – Lymph nodes – Lymphoid tissue: Peyer’s patches Organs of the Immune System Primary organs – Bone marrow – Thymus B lymphocytes T lymphocytes T lymphocytes B lymphocytes Three Notable Characteristics of Lymphocytes the Primary Immune Cells Specificity • Unique receptor on cell surface • Actual and only immunoglobulin that the cell is capable of making Clonality • One cell gives rise to others with same receptor • Group of cells with the same unique receptor Activation Activation – Triggered when lymphocyte encounters the antigen that matches its receptor – Cell enlarges, produces DNA, divides, and differentiates Notable Characteristics of Lymphocytes Specificity, Clonality, and Activation Molecules on surfaces of B & T lymphocytes B cells: immunoglobulin T cells: developmental antigens and specific receptors – Antigens related to cell function – T4 positive cells • Antigen makes cells prone to viral infection by the HIV virus that causes aids – depletion of this subset of t cells – T8 positive cells - suppressor cell ratio increases – (Macrophage - taxi for HIV) Molecules on Surfaces of B & T Lymphocytes B cells – immunoglobulin T cells developmental antigens and specific receptors B CELLS T CELLS Induction of response Accessory cells are required – Macrophage, dendritic cells, Langerhans’ cells Cell interactions with regulatory cells – Helper or suppressor T lymphocytes Induction of Response Peripheral organ needed to get antigen and responsive cell to interact – Lymphocyte recirculating – Appropriate context Effectors - B cells Dissemination of plasmablasts Antibody structure – specificity Switching of antibody classes How antibodies work? Dissemination of Plasmablasts Clonality One cell gives rise to others with same receptor to make a group of cells with the same unique receptor Antibody structure - specificity Antibody structure - specificity Unique receptor on cell surface Actual and only immunoglobulin that the cell is capable of making Switching of Antibody Classes Effectors - B cells How antibodies work? Roles and Specific Actions of Antibodies in Immunity Complement - mediated lysis Opsonization - promote phagocytosis Toxin neutralization Prevention of microbial binding to mucosal surface Virus neutralization - interferes with cell penetration Degranulation of mast cells Antibodies in Immunity Mast cells - allergic response Induced Degranulation of Mast cells Effector T cells Cytotoxic (killer) T cells Delayed - type hypersensitivity T cells Amplification – Factors (lymphokines) – Other cell types involved Effector T cells Cytotoxic (killer) T cells Effector T cells Cytotoxic (killer) T cells Effector T cells Delayed - type hypersensitivity T cells Amplification – Factors (lymphokines) – Other cell types involved Formed elements (non-fluid, cellular) and functions in blood Cell type Erythrocytes Main functions CO2 and O2 transport Neutrophils phagocytosis of bacteria Eosinophils parasitic infections, inflammatory processes release of histamine and other inflammation mediators Basophils Monocytes Mononuclear-phagocyte system become macrophages Formed elements (non-fluid, cellular) and functions in blood con’t Cell type B lymphocytes main functions generation of antibodyproducing plasma cells T lymphocytes killing of virus-infected cells Natural killer (cytotoxic T cell) killing of some tumor and virus-infected cells Platelets clotting of blood Lymphocytes Type B T lymphocyte Memory antigens Cytotoxic cells Helper cells Suppressor cells Function Plasma cells - antibodies Memory B cells T cell receptors specialized to recognize surface antigens of cells Sensitive to previous Destroys transplanted organs Secretes substances that help T & B respond Dampens response to foreign antigens and self antigens Macrophages Enhance the Immune Response Macrophages Enhance the Immune Response Lymph Nodes Filter Lymph Induction of the immune response requires: • Peripheral organ needed to get antigen and responsive cell to interact • Lymphocyte recirculating • Appropriate context Lymph Nodes Filter Lymph Lymphocyte Recirculating Lymph Nodes Filter Lymph Lymph Nodes Filter Lymph Lymph Nodes Filter Lymph Lymph Nodes Filter Lymph Amplification of the Immune Response: factors (lymphokines)and other cell types involved 1. Engulfing an invading organism and coupling with a helper T cell, a macrophage secretes the lymphokine interleukin (IL-1), which activates the helper T cell. IL-1 also stimulates the brain to raise the body’s temperature, causing fever, which enhances the activity of immune cells. 2. The activated helper T cell produces interkeukin-2 (IL2), which stimulates other helper and killer T cells to grow and divide. The helper T’s secrete a lymphokine called B-cell growth factor (BCGF) which causes B cells to multiple. 3. As the number of B cells increases, helper T cells produce another lymphokine, B-cell differentiation factor (BCDF), which instructs some of the B cells to stop replicating and start producing antibodies. 4. Helper T cells also produce a lymphokine called gamma interferon (IF), which has multiple effects. Like IL2, it helps to activate killer T cells, enabling them to attack the invading organism. Like BCDF, it increases the ability of B cells to produce antibodies. It also effects macrophages, keeping them at the site of the infection and helping them to digest the cells they have engulfed. Ontogeny Bone marrow Stem Cells: bone marrow Primary Lymphoid Organs Secondary Lymphoid Organs Differentiation to mature antigen: reactive cells Later: Lymphoid System Components, but now a little introduction Primary organs Secondary organs Primary organs Secondary organs (red blood cell linage) 112 Proerythroblast Polychromatophilic erythroblast Smear of bone marrow cells Primary organs Proerythroblast Erythropoietin is a colony stimulating factor for bone marrow in this linage (red blood cell precursors) Smear of bone marrow cells 123 Thymus, newborn Outer darkly staining areas (cortex) and lighter central areas (medulla). Medulla Cortex Thymocytes =T lymphocytes in the thymus Medulla Continuous capillaries, sheathed by epithelial reticular cells around each, characterizes blood vessels in the thymus cortex and is responsible for the blood thymus barrier. Also there are no afferent lymphatics in the thymus. 116 Lymph node Ref code # 5, 6 Large round structures (follicles), Cortex Medulla Germinal center, Subcapsulary sinus Afferent lymphatic duct Parafollicular region Parafollicular region 116 Follicle High endothelial venule Lymphoid Follicle = Site of lymphocyte entry into the lymph node (one way street) Typical flat endothelium 242 Esophagus and trachea, monkey Spleen Ref code #5 Venous sinuses, and Billroth's strands Capsule the red pulp. white pulp Primary function Of the spleen is filtration of blood. Spleen has no afferent lymphatics Central artery Spleen #19752 Litteral cells of spleenic venule 117 Spleen Penicillar arteries Billroth’s strand or spleenic strand Littoral cells: picketfence type endothelial cells of vascular sinus Life Cycle of Lymphocytes Fetal organs Bone marrow Primary lymphoid organs (Antigen independent development) - Thymus – T lymphocytes - Bone marrow - B lymphocytes Secondary lymphoid organs (Antigen dependent development) – Lymph nodes – Lymphoid nodules – Spleen Ref code #6

Overview of the Immune System

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