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Blood, part 2 Leukocytes, Immune System Basics, and Leukocyte Disorders Leukocytes (WBCs) • Only complete cells • < 1% total blood volume • Diapedesis: ability to leave blood vessels to move independently through tissues – Ex. loose CT or lymphoid tissues – Use amoeboid motion, following chemical trail released by damaged cells • Infections can increase WBC count to over 11,000 / mm3 – Normal WBC count ranges from 4800 – 10,800 Leukocyte Quantities (Most to least) Never Let Monkeys Eat Bananas Granulocytes • Include: – Neutrophils, Eosinophils and Basophils • Have membrane-bound granules: vesicles w/digestive enzymes and antimicrobial proteins • Granules can be visualized using Wright stain • Lobed nuclei • Larger than RBC; shorter-lived • Phagocytic Neutrophils • Most common WBC • Stain: – Granules stain w/ acidic (red) and basic (purple/black) Wright stain dyes – lilac colored cytoplasm • 2 Types of granules that lyse bacteria: – Lysosomes – Antimicrobial proteins: defensins • 3-6 lobes in nuclei • Kills Bacteria and Fungus • Slays bacteria w/aid of “respiratory burst” – O2 metabolized to create H2O2 and bleach Eosinophils • 2 – 4 % of WBCs • Red granules (acidic dye) – w/ lysosome-like digestive enzymes • Bi-lobed Nuclei • Kills mostly parasitic worms • Lessens allergies by phagocytizing immune complexes • Same size as Neutrophil Basophil • Rarest WBC (.5 – 1%) • Have U- or S- shaped nuclei • Purple/Black Granules (basic dye) – w/histamine that • • • Function like mast cells in CT Dilate vessels, increase inflammatory response Attracts other WBCs – w/heparin that • • • Promotes inflammation Increases heparin Acts as anticoagulant • Same size as neutrophil Agranulocytes • Include: – lymphocytes (T- and B- ) and monocytes: • Lack visible cytoplasmic granules – Have spherical or kidney-shaped nuclei • Major players in specific immune response. – – – – Recognize invaders Produce antibodies Attack viruses and tumors Act as phagocytic macrophages Lymphocytes • 25% of WBC • Large, dark-purple, circular nuclei with thin rim of blue cytoplasm • Found mostly in lymph nodes (some circulate in blood) • Two types : – T cells: • Helper T: coordinates immune response • Killer T: directly kills invaders, tumors, viruses – B cells: recognize invaders, make antibodies that bind, trap, and mark intruders for destruction Monocytes • • • • • 3-8 % of WBC Largest leukocytes Abundant pale-blue cytoplasm Purple-staining, U- or kidney-shaped nuclei Leave vessels, enter tissue, and become macrophages where they – actively phagocytize invaders marked by antibodies • Help activate lymphocytes by “presenting” the antigen of invaders they digest Summary of Leukocyte Histology Practice Identification Granulocyte Eosinophil Granulocyte Neutrophil Granulocyte Neutrophil Agranulocyte Lymphocyte Granulocyte Basophil Agranulocyte Monocyte More Practice Neutrophil Eosinophil Lymphocyte Basophil Monocyte Leukopoiesis (WBC Differentiation) Stem cells • Stem Cell Origin: Hematocytoblast • Myeloid Stem Cells: − − originate all WBCs except Lymphocytes • Myeloblasts and Lymphoblasts: − − “committed” lysosome formation begins Hemocytoblast Myeloid stem cell Committed cells Developmental pathway Myeloblast Myeloblast Promyelocyte Promyelocyte Eosinophilic myelocyte Basophilic myelocyte Neutrophilic myelocyte Eosinophilic band cells Basophilic band cells Neutrophilic band cells Basophils Neutrophils (c) Lymphoid stem cell Myeloblast Promyelocyte Promonocyte • Differentiation continues: − − granule accumulation lobing of nuclei Eosinophils (a) (b) Lymphoblast Prolymphocyte Monocytes Lymphocytes Some (e) become (d) Plasma cells Agranular leukocytes Granular leukocytes Some become Macrophages (tissues) What stimulates Leukopoiesis? • Interleukins (IL) and colonystimulating factors (CSFs) – act as chemical stimuli – Type and amount determines the type of leukocyte formed • Macrophages and T cells are most important sources of ILs and CSFs – released when a pathogen (disease causing organism) is detected Fun Fact: IL and CSFs often used to stimulate marrow of cancer patients Leukocyte Disorders: Leukemia • cancerous conditions of a “line” of WBCs • Acute leukemia: – blast-type cells – usually in children – progresses quickly • Chronic leukemia: – later stages of cyte-type cells – usually adults – progresses slowly • Named after cell type involved. Ex… – Myelocytic, Lymphocytic, Lymphoblastic leukemia Leukocyte Disorders: Leukemia • Bone marrow crowded out with cancerous, immatur leukocytes (no immune protection) Anemia Bleeding (Internal) Infections Fever, weight loss, pain Fatal Leukocyte Disorders: Leukopenia • Opposite of Leukemia • Abnormally LOW WBC count – Usually drug induced • ex. chemo• Glucocorticoids (steroids that suppress IS) – HIV infection