WBCs

What are the two major categories of WBCs

1. Granulocytes (Polymorphonuclear WBCs): Neutrophils, Eosinophils, Basophils.

2. Mononuclear Phagocytes: Monocytes and their tissue derivatives (Macrophages)

What are the roles of granulocytes?

Granulocytes play a vital role in innate immunity and inflammation by combating infections and mediating immune responses

What are the structural features and lifespan of neutrophils?

• Structure: Multi-lobed nucleus, granules containing microbicidal proteins.

• Lifespan: ~7 hours in blood, ~20 hours in tissues.

What are the key functions of neutrophils?

1. Eliminate bacteria and some fungi

   • Chemotaxis

   • Phagocytosis

What are the structural features and lifespan of eosinophils?

• Structure: Bilobed nucleus, granules containing major basic protein.

• Lifespan: 8–12 hours in blood, 8–12 days in tissues

What are the key functions of eosinophils?

1. Combat parasitic infections.

2. Mediate allergic inflammation.

3. Mechanism: Antibody-dependent cell-mediated toxicity

What are the characteristics of basophils (rarity, lifespan, function, stimuli)?

• Rarity: Very few in number; highly motile.

• Lifespan: Hours to days.

• Function: Release histamine and cytokines in allergic responses.

• Stimuli: Activated by IgE, IL-3, C5a, GM-CSF.

What are the structural features and lifespan of monocytes?

• Structure: Kidney-shaped nucleus, cytoplasmic granules.

• Lifespan: ~24 hours in blood; longer as macrophages in tissues

What are the primary functions of monocytes?

1. Phagocytosis of pathogens and debris.

2. Antigen presentation to T cells via MHC class II.

3. Cytokine secretion (e.g., G-CSF, GM-CSF).

How do granulocytes mature?

1. Stem cells migrate to different tissues to differentiate

2. Blasts → Promyelocytes → Myelocytes → Metamyelocytes → Band forms → Mature granulocytes

3. regulated by cytokines

What is hypereosinophilic syndrome?

Sustained eosinophilia causing tissue damage in organs such as the heart and CNS

What are examples of monocyte-related disorders?

lipid storage disease, monocytosis

How is WBC function tested?

1. Nitroblue Tetrazolium (NBT): Detects respiratory burst activity in neutrophils.

2. Phagocytosis Assays: Measure the ability to engulf and kill bacteria.

3. Motility Tests: Assess migration through membranes.

   • Increasingly replaced by flow cytometry