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 / mm 3 – 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” – O 2 metabolized to create H 2 O 2 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 Agranulocyte Lymphocyte Agranulocyte Monocyte Granulocyte Basophil Granulocyte Eosinophil Granulocyte Neutrophil

More Practice NeutrophilEosinophilBasophil LymphocyteMonocyte

Leukopoiesis (WBC Differentiation) (a) (b)(c) (d) (e) Myeloid stem cellLymphoid stem cell Myeloblast Lymphoblast Stem cells Committed cells Promyelocyte PromonocyteProlymphocyte Eosinophilic myelocyte Neutrophilic myelocyte Basophilic myelocyte Eosinophilic band cells Neutrophilic band cells Basophilic band cells Develop- mental pathway EosinophilsNeutrophilsBasophils Granular leukocytes Plasma cells Some become Monocytes Lymphocytes Macrophages (tissues) Agranular leukocytes Some become Stem Cell Origin: Hematocytoblast Myeloid Stem Cells: −originate all WBCs −except Lymphocytes Myeloblasts and Lymphoblasts: −“committed” −lysosome formation begins Differentiation continues: −granule accumulation −lobing of nuclei Hemocytoblast

What stimulates Leukopoiesis? Interleukins (IL) and colony- stimulating 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, immature 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