Hematology Quiz: Immune Cells and Conditions

White Blood Cells (Leukocytes)

• WBCs are nucleated cells that perform the body's defense functions.
• They destroy invading microorganisms and abnormal cells, like cancer cells.
• After blood centrifugation, WBCs are found in the buffy coat, a thin white layer between the sedimented red blood cells (RBCs) and plasma.
• Plasma makes up 55% of total blood volume.
• Buffy coat, which includes leukocytes and platelets, accounts for less than 1% of total blood.
• Erythrocytes (RBCs) account for 45% of total blood.

Normal Values

• Adults: Normal WBC count ranges from 4,000 to 11,000 per cubic millimeter (mm³) of blood.
• Newborns: Normal WBC count ranges from 10,000 to 25,000 per mm³ of blood. The count decreases after the second week and reaches the normal adult value between 5 and 10 years of age.

Differential Count

• Specific WBC types have varying absolute and relative counts.
• Neutrophils: 3,000-6,000 /cu.mm, 50-70%
• Eosinophils: 150-300 /cu.mm, 1-4%
• Basophils: 10-100 /cu.mm, <1%
• Lymphocytes: 1,500-2,700 /cu.mm, 20-40%
• Monocytes: 300-600 /cu.mm, 2-8%

WBC Count Variations

• Leukocytosis: An increase in WBC count above 11,000/mm³.
  • Physiological causes: Newborn, exercise, mental stress, pregnancy, and after food intake.
  • Pathological causes: Acute bacterial infections, acute hemorrhage, burns, and tuberculosis.
• Leukopenia: Decrease in WBC count below 4,000/mm³.
  • Causes: Typhoid fever, starvation, viral/protozoal infections, and bone marrow depression.

Classification of White Blood Cells

• Granulocytes: Contain granules in their cytoplasm.
  • Neutrophils
  • Eosinophils
  • Basophils
• Agranulocytes: Lack granules in their cytoplasm
  • Lymphocytes
  • Monocytes

Morphology (Neutrophils)

• Size: 10-14 µm in diameter.
• Nucleus: Young neutrophils have a horseshoe shape. Mature neutrophils have a multi-lobed nucleus (2-6 lobes).
• Cytoplasm: Granular, slightly bluish-pink color.
• Granules: Contains enzymes (lysosomal) such as glycosidases.
• Fine sand-like particles capable of taking both acidic & basic stains.

Morphology (Eosinophils)

• Size: 10-14 µm in diameter
• Nucleus: Bilobed, often described as a spectacle shape
• Cytoplasm: Acidophilic (eosinophilic stain), light pink
• Granules: Coarse, strongly stain red with eosin. Contains various chemicals like major basic protein, eosinophil cationic protein, peroxidase, and neurotoxin.

Morphology (Basophils)

• Size: 10-14 µm in diameter
• Nucleus: Bilobed, often obscured by granules, S-shaped
• Cytoplasm: Slight basophilia, blue color
• Granules: Coarse, stain dark purple or blue with methylene blue. Granules over crowd the nucleus. Contains histamine, heparin, serotonin, and eosinophil chemotactic factor.

Morphology (Lymphocytes)

• Size: Large lymphocytes—10–14 µm; Small lymphocytes—7–10 µm.
• Nucleus: Large, round, or slightly indented. Occupies most of the cell, leaving little cytoplasm around the edges. Purple.
• Cytoplasm: Pale blue, scanty.

Morphology (Monocytes)

• Size: 10-18 µm largest WBC type.
• Nucleus: Single, round or indented, eccentrically located
• Cytoplasm: Pale blue, clear. Sometimes contain fine granular structures (azurophilic granules).

Functions (Neutrophils)

• Actively phagocytic, first line of defense against acute bacterial infection.
• Release endogenous pyrogens – fever mediating substances.
• 4 stages in their lifecycle: marrow pool, circulation pool, marginated pool, tissue pool.

Functions (Eosinophils)

• Participate in defense against helminthic (parasitic) infections.
• Attack parasites too large for phagocytosis; release toxic enzymes (peroxidase).
• Involved in allergic reactions – collect at sites of reaction to limit histamine effect.

Functions (Basophils)

• Phagocytic – but less efficient than neutrophils or monocytes.
• Release histamine and ECF-A (eosinophil chemotactic factor of anaphylaxis) during allergic reactions, contributing to allergic reactions and inflammation.
• Release heparin, which has anticoagulant properties.

Functions (Lymphocytes)

• Divided into B cells, T cells, and NK cells.
• B cells: Secrete antibodies mediating humoral immunity.
• T cells: Mediate cell-mediated immunity.
• NK cells: Mediate natural and non-specific immunity.

Functions (Monocytes)

• Active phagocytes, second line of defense.
• Important antigen-presenting cells (APCs).
• Secrete chemokines with varied roles.

Lifespan (Neutrophils)

• 4 life stages: Marrow pool, Circulation pool (8-10 hours), Marginated pool, Tissue pool. Usually only survive in tissue pool for 4-5 days.

Variations (Neutrophils, Eosinophils, Basophils, Lymphocytes, Monocytes)

• Neutrophils: Neutrophilia (increased count), Neutropenia (decreased count).
• Eosinophils: Eosinophilia (increased count), Eosinopenia (decreased count)
• Basophils: Basophilia (increased count), Basopenia (decreased count)
• Lymphocytes: Lymphocytosis (increased count), Lymphocytopenia (decreased count).
• Monocytes: Monocytosis (increased count), Monocytopenia (decreased count)

Phagocytosis

• Process of ingestion and killing of microbes or foreign matter by phagocytes.
• Stages: Chemotaxis, Diapedesis, Adherence, Ingestion, and Killing.