Blood Cells and Hemopoiesis

Lecture title: blood cells and hemopoiesis 28/2/2022 Leukocytes 2 Leukocytes • Originate in the bone marrow and released continuously into the blood • Travel in bloodstream but function mainly OUTSIDE blood vessels (in loose CT) • Leukocytes form a mobile army that helps protect the body from damage by bacteria, viruses, parasites, toxins and tumor cells • 5 types organized into 2 groups depending on nuclear shape and cytoplasmic granules –Granulocytes (single, multi-lobed nucleus) I. Neutrophils II. Eosinophils III. Basophils –Agranulocytes (mononuclear leukocyte) I. Lymphocytes II. Monocytes 3 Sheet Note 1 - Red bone marrow → main function is production of blood . - Yellow bone marrow is filled with adipose tissue and it doesn’t produce blood. - Function of leukocytes is outside the circulation, they function in the connective tissue - monocytes +lymphocytes granules Both types have granules but the granulocytes have special(specific ) granules. The agranulocytes have only lysosomes(primary granules) Multi-lobed nucleus (but single) is associated → granulocytes Mononuclear is associated → agranulocytes Leukocytes, or WBCs, are nucleated and subdivided into granulocytes and agranulocytes, depending on the presence or absence of specific granules in their cytoplasm These specific granules multi-lobed nucleus multinucleated chromatin ‫ن‬ stain red with acidic stain Large granules, acidophilic → pink granules Neutral affinity for both dyes, so the granules are such as eosin barely seen small granules Large granules, basophilic → deep blue granules Single nucleus, multi-lobed nucleus These specific granules stain with basic stain Nonspecific granules → lysosomes → stained by azure dye → azurophilic Lysosomes=Primary granules= Nonspecific granules 5 Lymphocyte play a key role in all immune responses, in contrast to the other leukocytes their activity is always directed against specific foreign agents All the leukocytes perform their function in the tissues and merely use the blood asa vehicle for transit between sites of formation, storage,activity Neutrophils and monocytes are highly phagocytic and engulf micoorganisms, cell debris in a non-specific manner. 6 Cytoplasmic granules Agranulocyte Specific granules Secondary granules Non-specific granules Azurophilic granules Lysosomes All the same name for the same gran Primary granules Granulocytes • Cytoplasmic granules (containing enzymes or chemicals) →makes cytoplasm look grainy • Single multi-lobed nucleus (segmented) • All are phagocytic; they engulf and consume foreign cells and material • 3 main types: The granules are hardly seen? Because it doesn’t have specific affinity for dyes It needs high magnification to be seen. Small granules, pale pink/salmon pink Large granules, Red Large granules, blue 7 Neutrophil • The most common leukocyte in blood • constitute 40-75% of circulating leukocytes • Characterised by the shape of the nucleus which contains small lobed connected by thin filaments • When mature there are usually 5 lobes connected by fine strands of nuclear material. In less mature neutrophils the nucleus is less lobulated • 2-5 lobes in nucleus connected by “threads” of nuclear material (polymorphs) Same name for neutrophiles in clinical application Light pink cytoplasm • • Called neutrophils because cytoplasm takes up red (acidic) and blue (basic) stains equally The specific granules color is light pink The number of lobes of the neutrophiles differs from to other according to AGING → ( 2 lobes) → at site of infection (5 lobes) site of infection 8 • 1. 2. 3. Specialized for responding to: bacterial invasions Acute infections acute pyrogenic infections Pyrogenic = infections with (fever • Neutrophils are short-lived cells with a half-life of 6-8 hours in blood and a life span of 1-4 days in connective tissues before dying by apoptosis. Half life in tissues → Days(dies by apoptosis), Half life in circulation → hours 9 Neutrophils are the first WBCs that leave the blood in large numbers to reach the site of inflammation Cells of acute infection 1-The most abundant 2-The most motile 3-Neutrophil chemotactic factors (chemotaxins) are the first released How to know that this blood sample is from female? Sheet note -Ans: Drumstick like appearance (structure), which is due to Barr body (the inactive X of the female (xx) sex chromosomes -Can there be a 2 Barr bodies? Ans: Yes, in super female case (xxx), because it’s must be only one active (X) In females, the inactive X chromosome (Barr body) may appear as a drumstick-like appendage on one of the lobes of the nucleus (about 3% of neutrophils in peripheral blood) 10 Granules in neutrophils • Specific granules (secondary) • Azurophilic granules (primary) ‫اكبر حجما واقل عددا‬ (most numerous) (less numerous) Small in size Lysozyme not lysosome Somewhat larger in size -Lysozyme: act against cell wall -Myeloperoxidase (bacteriocidal) -Phagocytin (bactericidal) -Acid hydrolase -Lactoferrin (bacteriostatic) -Defensins -Collagenase And elastases to gain ability to cross the site of infection (barely visible by light miscroscopy) Bactericidal=destruction and killing Bacteriostatic=stops the differentiation of the pathogen Pus cells → pus is anaerobic environment and it formed after the bacterial infection, so the ability of neutrophiles to work at this condition gave it this name. (it generates power by glycolysis) Different names for neutrophils: Polymorphs Naming reason: the changing of number of lobes according to maturation Pus cells Micro not macro, serves the same function as macrophages Microphages Cells of acute inflammation The ability of neutrophils to survive in an anaerobic environment is highly advantageous, because they can kill bacteria and help clean up debris in poorly oxygenated regions, for example, damaged or necrotic tissue lacking normal microvasculature 11 Neutrophilia: • increase in the number of neutrophils in the circulation • this does not necessarily imply an increase in neutrophilproduction Intense muscular activity and administration of epinephrine can produce APPARENT neutroplelia they causes neutrophils in the marginating compartment to move into the circulating compartment Glucocorticoids: increase the mitotic activity of neutrophil precursors in the marrow → increase blood count of neutrophils Neutrophilia that occurs during bacterial infections → increase production of neutrophils for short duration of these cells in bone marrow Neutropenia → Decrease in number of neutrophiles. Neutrophilia DOESN’T always indicate a pathologic condition. Because the neutrophiles are found at different pools outside the circulation in exercise and stress conditions, the neutrophiles travel to the circulation. and after the (stress, exercise) stops the neutrophiles return to the pools. 12 Eosinophils Less compared to neutrophiles • Accounts for 1-6% of leukocytes in circulating blood Like glasses ‫زي النظارة‬ • Usually have bi-lobed nuclei connected by a short “thread” of nuclear material • Large cytoplasmic granules, which stain red with the acidic eosin dye • Functions: • Eosinophils are phagocytic cells but less bacteriocidal than neutrophils • Eosinophils have a particular phagocytic affinity for antigen-antibody complex • Help in ending allergic reactions and in fighting parasitic infections • All eosinophils have receptors for IgE (important in the destruction of parasites, this is not present on neutrophils 13 During allergic reactions Eosinophils undergo chemotaxis in response to histamine and eosinophil chemotactic factor of anaphylaxis (ECF-A) released from basophils and mast cells To end allergic reaction . Eosinophils ameliorate some aspects of hypersensitivity reactions They neutralise histamine and produce a factor (eosinophil-derived inhibitor) which inhibits mast cell degranulation Eosinophilia: increase number of circulating eosinophils are found in 1 many types of parasitic disease (defense against parasites is one of their principle functions) 2 in some allergic disease such as hay fever and asthma 14 Specific granules (Crystalloid granules): Specific granules in eosinophiles -Oval in shape, with flattened crystalloid cores histamine‫يوقف ال‬ heparin ‫يوقف ال‬ -Two parts: 1 Externum(pale):contains histaminase and sulfatase 2 Internum(dark):contains basic protein to kill parasites The eosinophils granules are lysosomes and contain the usual lysosomal enzymes, they show a higher content of peroxidase than do the azurophilic granules of neutrophils and lack lysozyme and phagocytin For parasitic infections Crystalloid granule 15 Basophils • Rarest leukocyte –might not see these under the microscopes (less than 1%) Very large specific granules, blue in color, which covers the nucleus • Usually have bi-lobed, S-shaped nuclei obscured by the large basophilic granules ‫ زي النظارة‬Eosinophils ‫ ال‬S shaped ‫هاي‬ • Has large granules that stain dark purple/ blue in basic dyes (basophil= basic loving) • Granules contain histamine, heparin and eosinophilic chemotactic factor that mediate inflammation in allergic reactions and parasitic infections Initiate allergic reaction ECF-A 16 Both basophils and mast cells have surface receptors for immunoglobulin E (IgE), and secrete their granular components in response to certain antigens and allergens. To initiate immune reaction Mast cell blood stream connective tissue basophiles ‫االختالف بينهم مكان التواجد‬ mast cells Basophils account for up to 15% of infiltrating cells in allergic dermatitis and skin allograft rejection allergic reaction? -in skin dermatitis → basophiles increase from 1% to 15% 17 Plasma cells lymphocyte differentiate Exposure may be by ingestion, inhalation, injection, or direct contact Antibodies - IgE Allergen antigen In some individuals substances such as certain pollen proteins or specific proteins in food are allergenic, that is, elicit production of specific IgE antibodies, which then bind to receptors on mast cells and immigrating basophils. Upon subsequent exposure, the allergen combines with the receptor-bound IgE molecules, triggering rapid exocytosis of the cytoplasmic granules. allergic reaction degranulation of basophils bridging antibody(IgE) with the antigen Release of the inflammatory mediators in this manner can result in bronchial asthma, cutaneous hives, rhinitis, conjunctivitis, or allergic gastroenteritis. Immediate or type 1 hypersensitivity In some individuals a second exposure to a strong allergen, such as that delivered in a bee sting, may produce an intense, adverse system in the body systemic response. Anaplylactic shock Basophils and mast cells may rapidly degranulate, producing vasodilation in many organs, a sudden drop in blood pressure, and other effects comprising a potentially lethal condition called Anaphylaxis or anaphylactic shock. 18 Agranulocytes Just primary granules- not lobulated. • Single non-lobulated nucleus • Granules in cytoplasm are too small to see (nonspecific granules, azurophilic granules, primary granules, lysosomes) •2 types based on structure (not cell lineage): –Lymphocytes –Monocytes 19 Monocytes • Largest leukocytes • Constitute 2-10 % of leukocyte in peripheral blood •Bluish cytoplasm (frosted glass appearance)& a large Cshaped nucleus • Highly motile and phagocytic •Travel through bloodstream to reach connective tissues, where they transform into macrophages (large phagocytic cells) macrophage • Chronic infections Are precursor cells of macrophages, osteoclasts, microglia, and other cells of the mononuclear phagocyte system in connective tissue All monocyte-derived cells are antigen-presenting cells To recognize the receptors. 20 MONONUCLEAR PHAGOCYTIC SYSTEM ( all characterized by phagocytic activity) osteoclasts Bone Kupffer Cells liver Microglia CNS Dust cells lung Pulmonary macrophage Dendritic cells Lymph node spleen macrophages Bone marrow Connective tissue Langerhans cells epidermis No specific name for them Are found in skin, because the skin is the first defensive system. 21 Lymphocytes • Smallest leukocytes (slightly larger than erythrocytes) •The second most common leukocyte in circulating blood and make up 20-25% of differential white cell count • Round nucleus occupies most of cell volume • Cytoplasm is light clear blue • Increased numbers are commonly seen in viral infections 23 Lymphopoiesis: the process by which lymphocytes are formed In bone marrow* Precursor cells in bone marrow But they are still, immunocompetent(inactive) which are capable to differentiate between self and non self antigen. active ‫بس اذا راحت عالدم بتصير طوالي‬ Thymus T Lymphocytes Bone Marrow B Lymphocytes Directly into blood Natural killer lymphocytes 24 The amount of cytoplasm depends upon state of activity of the lymphocyte, in circulating blood there is: When in it is inactive, slightly larger than erythrocyte (and small rim of cytoplasm with large nucleus) 1 Predominance of small inactive lymphocytes (6-9 μm in diameter) 2 Large lymphocytes (9-15 μ m) make up about 3% of lymphocytes in peripheral blood When it becomes active the cytoplasm becomes less dark-blue, and the amount of cytoplasm increased represent activated lymphocytes en route to the tissues where they will become antibody-secreting plasma cells, they also include natural killer cells In the large lymphocyte → the cytoplasm is readily visible but in the small lymphocyte the cytoplasm is almost too sparse to be seen (contain few mitochondria, rudimentary golgi apparatus, minimal endoplasmic reticulum but large number of ribosomes→ account for basophilia (blue cytoplasm) Can be differentiated to T or B lymphocyte Active lymphocyte of natural killer cells 25 •Lymphocytes vary in life span according to their specific function, some live for a few days and some live for many years Unlike the macrophages and neutrophiles immunity which it’s immunity name(innate immunity) (which do the phagocytosis to all antigen Cell mediated immunity • T cells –Has different types, some directly kill foreign or infected cells; others activate phagocytes to destroy microbes Lymphocytes → highly specific, adaptive immunity response for specif antigens Humoral immunity • B cells –Differentiate into plasma cells –Secrete antibodies that bind to specific antigens and mark them for destruction by phagocytic cells Long term immunity Do B lymphocytes go to site of infection? No, but send the antibodies to site of infection (naming reason (humoral immunity ‫))االستجابة السائلة‬ 26 Neutrophils and monocytes are highly phagocytic and engulf microorganisms and cell debris in a NON-SPECIFIC manner (Innate immunity) While the activity of lymphocytes is always directed against SPECIFIC foreign agents (Adaptive immunity) The small lymphocyte has scanty cytoplasm (contain few organelles but large number of ribosomes ) Account for basophilic 27 Innate immunity: We are born with innate immunity. It is non-specific, which means that the innate cells are not able to distinguish one type of pathogen from another. Adaptive (acquired) immunity: is the body's ability to recognize and respond to specific foreign substances (antigens: microbes, parts of microbes, or non-microbial substances, such as pollen) Cells of innate immunity: Neutrophils, Basophils, Eosinophils, Mast cells, Monocytes (macrophages and dentritic cells), natural killer cells Cells of adaptive immunity: B and T lymphocytes 28 Immunocompetent in bones marrow Immunocompetent in thymus Plasma cell (produce antibodies) Kill virus infected, transplanted and neoplastic cells (innate immunity) Memory cell Any cell that doesn’t present MHC-1 antigen, will recognize it as abnormal cell and destroy it ***I think MHC-1 is the self antigin To memorize the antigen, the directly produce antibodies, the principle of vaccination. Cytotoxic Kill virus-infected, transplanted and neoplastic cells (adaptive immunity) Helper Help cytotoxic T cells and B cells in their immune function Suppressor Suppresses immune response to self Ag Suppresses immune response of T and B lymphocytes Can work as APC to active B and T After the infection ends, those cells come and inactive T and B. If there is a problem in these cells there 29 will be an immune disease. Suppressor T cells switch off the immune response when the stimulus is removed Damage to suppressor cells can result in autoimmune disease Memory cells allow a more rapid response if the antigen appears again later which allows a very rapid response upon subsequent exposure to the same antigen. Basis of immunity/vaccination Natural killer cells and T cells play a major role in graft rejection 30 31 Thrombocytes (Platelets) Cytoplasm • Small non-nucleated cytoplasmic fragments • Formed by fragmentation of the cytoplasm of megakaryocytes in the bone marrow •Number: 200,000-400,000/mm3 •Shape: biconvex discs •Cytoplasm: purple, granular •Diameter: 2-4 um •Lifespan about 10 days 33 34 Sheet Note 3 - In bone marrow → sinusoidal capillaries → there is processes of megakaryocyte which have cytoplasmic processes → The blood flow causes the fragmentation of these cytoplasmic processes → and this fragments are the platelets •Control the bleeding by plugging the defects in blood vessels and activating blood clotting cascades In stained blood smears, platelets often appear in clumps Platelete has 2 zones 1 Outer pale basophilic (clear) perpheriral zone: In stained blood smears, platelets often appear in clumps Hyalomere (smooth, glassy like, likely hyaline) 2 Central dark granular zone: granulomere 36 Hyalomere: contains cytoskeleton and membranous channels Cytoskeletal elements • Microtubule • Actin filaments Membrane channels • Open canalicular system • Dense tubular system Invaginations from plasma membrane to granulomere To increase surface area of exchange and make it easier Contains Ca+2 (calcium for blood clotting) Maintain shape and help contractions of platelets and squeezing Granulomere: contains granules and organelles Alpha granules: clotting factors, growth factors Dense (delta) granules: serotonin (absorbed from plasma), ATP, ADP Lambda granules: lysosomes (aid in clot resorption) 37 Their main function is to continually monitor the vascular system and detect any damage to the endothelial lining of the vessels. If the endothelial lining breaks, the platelets adhere to the damaged site and initiate a highly complex chemical process that produces a blood clot→ Thus preventing blood loss Due to the sugars on the surface of platelets they get stick to each other 38 Hemopoiesis Hemopoiesis Prenatally Postnatally 1- Mesoblastic phase: in mesoderm of yolk sac (2nd -6th) weeks of pregnancy Hemopoietic stem cell forms Mostly* 2- Hepatic phase: within the liver and spleen also play a role in second trimester The reason why Occurs almost exclusively in bone marrow: Sternum, ribs, pelvis, proximal ends of femur, vertebrae liver get enlarged at this stage: 3- Myeloid phase: in bone marrow begins in the 3rd trimester Red bone marrow Formation of blood cells in bone marrow → medullary hemopoiesis outside bone marrow → extra medullary hemopoiesis. All the blood is from one cell called: Pluripotent hemopoietic stem cells It is believed that ALL blood cells arise from a single type of stem cell in the bone marrow called a pluripotent stem cell This cell can produce all blood cell types Means all potential → potential to give all types of blood cells Proliferate and form TWO major cell lineages: one for myeloid cells granulocytes, monocytes, erythrocytes, megakaryocytes One for lymphoid cells (lymphocytes) all develop in bone marrow All white cells (except lymphocytes),erythrocytes and platelets All happens in red bone marrow Early in their development, lymphoid cells migrate from the bone marrow to thymus or to the lymph nodes, spleen, and other lymphoid structures where they proliferate and differentiate Pluripotent CFU: colony forming unit Stem cells Lymphoid stem cell (Multipotent) Myeloid stem cell (Multipotent) Multiple type of cells Progenitor cells (committed, unipotent stem cells) CFU-M Unipotent CFU-L Mature cells NK Lymphoblast T Lymphoblast Precursor cells B Lymphoblast G=Granulocyte M=Monocyte Monoblast M=Megakaryocyte CFU-G Myeloblast Erythroblast E=Erythtocyte CFU-M Megakaryoblast CFU-E Sheet Note 4 - When the stem cells duplicates it gives rise to another stem cell, to save and keep a reserve of it, the progenitor cell does the same. But the precursor cell only give rise to mature cell it never gives rise to precursor cell, because it’s not a stem or progenitor cell. Progenitor and precursor cells: the pluripotent stem cells give rise to daughter cells with restricted potentials called: Progenitor cells or colony-forming units → CFUs (since they give rise to colonies of ONLY ONE cell type when cultured or injected into spleen) Progenitor cells are 4 types: A- Erythroid lineage of CFU-erythrocytes (CFU-E) B- Thrombocytic lineage of CFU- megakaryocytes (CFU-Meg) C- Granulocyte-monocyte lineage of CFU- granulocyte- monocytes (CFU-GM) D- Lymphoid lineage of CFU- lymphocytes of all types (CFU-L) All four progenitor/ CFUs produce → precursor cells or blasts Where morphologic characteristics begin to differentiate suggesting the mature cell types they will become Stem cells and Progenitor cells cannot be morphologically distinguished and resemble large lymphocyte Rate of cell division : slow in stem cells rapid in progenitor and precursor cells Progenitor cells: can divide and produce both progenitor cells and precursor cells Precursor cells: produce only mature blood cells 1-Potentiality is the potential to give rise to more than one type of cell 2-mitioc activity is the highest at precursor cells and mature cells don’t divide 3-you can’t differnitae between the blood cells until they reach the mature cell phase ( even at precursor cell(blast phase) the cells almost the same E.g. T,B and natural killer cells are derived from lymphocytes. 4-self renewing 5-differentiated functional activity: Stem cells are capable of asymmetric division and self-renewal Stem cells can maintain the original population Precursor cells produce only mature blood cells Erythroblast Every time the stem cell multiplies, it will give two cells, one differentiate into mature RBCs and the other cell add to the original population STEMcell gives rise to erythrocytes and renew itself by giving rise to another stem cell All erythroblasts multiply and differentiate into mature RBCs (erythrocytes) and no erythroblasts are left in the end erythroBLAST it will only give rise to erythrocytes it will not give erythonlast Or renew itself