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Physiological Functions of White Blood cells

Physiological Functions of White Blood cells. Objectives: WBCs Identify the different types of WBCs Enumerate the functions of the various types of WBCs Describe the steps of formation of WBCs List the factors required for their maturation.

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Physiological Functions of White Blood cells

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  1. Physiological Functions of White Blood cells

  2. Objectives: WBCs • Identifythe different types of WBCs • Enumerate the functions of the various types of WBCs • Describe the steps of formation of WBCs • List the factors required for their maturation. • Infer the importance of total and differential WBC counts • Define the terms leucocytosis and leucopenia • Define leukemia

  3. White Blood Cells (WBCs) Total Leucocyte count (TLC) 4000-11,000 /μL Types of WBCs Granulocytes contain granules Neutrophils Eosinophils Basophils: Agranlocytes Lymphocytes Monocytes Differential count: DLC Neutrophils 60-70% Lymphocytes 20-25% Monocytes 3-8% Eosinophils 1-4% Basophils 0-1%

  4. Neutrophils 60-70% • 10-12 µ in size; 2-5 lobed nucleus; Older the cell more the lobes- • (polymorphonuclear leukocytes); • Small colored granules which contain enzymes, Defensins, oxidants • Action: by Phagocytosis • Life span: a few hrs: 4-8 hrs in blood; 4-5 days in tissues • Fast response; neutrophilia in bacterial diseases; neutropenia in drug toxicity Eosinophils 0-4%; 10-12 µ Bi-lobed nucleus; coarse acidophilic granules Phagocytose antigen-antibody complexes; destroy parasites Granules contain various enzymes : MBP Increase in allergic conditions; decrease during stress-corticoids Basophils 0-1% 8-10 µ Nucleus usually bi-lobed; large deep purple colored granules which often cover the nucleus Secrete heparin, serotonin, histamine: help in inflammation The Granulocytes

  5. Agranular WBCs Monocyte 12-20 µ;3-8%; circulate in blood for about 20-30 hrs. long life span (many weeks to months) after change into macrophages in tissues Single kidney shaped nucleus Phagocytosis after converting in to macrophages Lymphocyte 6-9 µ (small); 10-14 µ (large); 20-25%; mostly formed in lymhoid tissue; some in bone marrow. Nucleus surrounded by thin ring of cytoplasm; long life span inside tissues, but only a few hours in blood B and T lymphocytes:Immune mechanisms B lymphos form plasma cells Natural Killer (NK) cells against viruses, cancer

  6. Physiology and Functions of WBCs • Life span: few hours to a few days • They have Major Histocompatibility Antigens on surface: -Identification of the “SELF” • Main functions: • combat infection by phagocytosis • immune mechanisms • Adhesion molecules • Selectins:on endothelial cells - attach to CHOn on neutrophil surface • Integrinson neutrophils: also make WBCs stick to endothelial surface, & help them to move out of the blood vessels • When required , they escape from the blood via capillary pores (emigration) helped by integrins enter tissue and have their action there by phagocytosis

  7. Phagocytosis • Mainly by neutrophils and monocytes • Steps of Phagocytosis 1 . Chemotaxis :attraction of WBCs to site of infection Promoted by i. bacterial toxins ii. kinins from damaged tissues iii. CSFs 2. Adherence phagocyte attaches to microbe using proteins 3.Ingestion pseudopods from WBC surrounds microbe formation of a PHAGOSOME

  8. 1 CHEMOTAXIS Microbe Phagocyte 3 INGESTION 2 ADHERENCE Pseudopod 4 DIGESTION Lysosome Digested microbe in phagolysosome Plasma membrane Residual body (indigestible material) 5 KILLING Digestive enzymes Phases of phagocytosis 4. Digestion Phagosome enters cytoplasm of WBC and merges with LYSOSOME: Phago-lysosome: secretion of lysozomal enzymes followed by release of oxidants: oxidative burst 5. Killingas result of the above. Residual bodies get left behind

  9. Formation of WBCs: Hemopoiesis

  10. Pluripotent stem cell Lymphoid stem cell Myeloid stem cells Colony Forming Unit G/M T lymphocyte T lymphoblast Neutrophil monocyte Eosinophilic myeloblast B lymphocyte B lymphoblast eosinophil NK Cell NK lymphoblast Basophilic myeloblast basophil • Granulocytes and monocytes : formed only in the BONE MARROW stored in the bone marrow, and • released into circulation. Lympocytes and Plasma cells also in lymhoid tissue, are stored in lymhoid • tissue . Few released into circulation • Various Colony Stimulating factors (CSFs or Growth Inducers) help in their formation: • IL1, IL6 and IL3 (multi CSF) • These are proteins in nature

  11. Normal WBC count: 4000-11000 Leuocytosis >11000 Leuopenia < 4000 Neutophils Infections, Burns, inflammation Lymphocytes Viral infections Monocyts Viral, fungal infections, TB, Chronic disease Eosinophils Some viral infections Bacterial infections (typhoid) Bone marrow suppression Drugs: antibiotics corticosteroids

  12. Typical eg: 8 year child; high fever; pain throat; difficulty in swallowing swollen septic tonsils TLC 18,500 DLC: N. 88%; L 10%; E 2% Elderly person; exposure to radiation Hx of intractable fever and infections; Loss of appetite TLC 2000 DLC: N. 30% L 60%; E 4% ; 6% other WBCs Leukemias (blood cancer)

  13. Summary 1. TLC, types of WBC, DLC 2. Description of various types of WBCs and their actions 3. Phagocytosis 4. Development of WBCs and factors associated 5. Define leucocytosis/leucopenia with typical examples 6. Leukemias or blood cancer

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