Blood, part 2 Leukocytes, Immune System Basics, and Leukocyte Disorders
Dec 18, 2015
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)
NeverLet MonkeysEatBananas
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
Agranulocyte Lymphocyte
AgranulocyteMonocyte
GranulocyteBasophil
GranulocyteEosinophil
GranulocyteNeutrophil
GranulocyteNeutrophil
More Practice
Neutrophil Eosinophil Basophil
Lymphocyte Monocyte
Leukopoiesis (WBC Differentiation)
(a) (b) (c) (d) (e)
Myeloid stem cell Lymphoid stem cell
Myeloblast MyeloblastMyeloblast Lymphoblast
Stem cells
Committedcells
Promyelocyte PromyelocytePromyelocyte Promonocyte Prolymphocyte
Eosinophilicmyelocyte
Neutrophilicmyelocyte
Basophilicmyelocyte
Eosinophilicband cells
Neutrophilicband cells
Basophilicband cells
Develop-mentalpathway
Eosinophils NeutrophilsBasophils
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)
AnemiaBleeding (Internal)InfectionsFever, weight loss, painFatal
Leukocyte Disorders:Leukopenia
• Opposite of Leukemia• Abnormally LOW WBC count– Usually drug induced • ex. chemo-• Glucocorticoids (steroids that suppress IS)
– HIV infection