Q.33 Which of the following immune cells are known as polymorphonuclear (PMN) leucocytes?
(1) Macrophages
(2) Neutrophils
(3) Monocytes
(4) Eosinophils
Which Immune Cells Are Polymorphonuclear PMN Leucocytes: Neutrophils Explained
Polymorphonuclear leukocytes (PMNs) refer to white blood cells with multi-lobed nuclei, crucial for innate immunity. This SEO article resolves the MCQ for biology and immunology students preparing for exams.
Correct Answer
The correct answer is (2) Neutrophils. Neutrophils are the primary polymorphonuclear leukocytes, characterized by their multi-lobed nucleus (3-5 lobes) and cytoplasmic granules, making up 50-70% of circulating WBCs [ from prior context on immunology].
Role in Immunity
Neutrophils act as first responders in acute inflammation, performing phagocytosis, releasing antimicrobial granules, and forming NETs (neutrophil extracellular traps) to combat bacteria and fungi. Their PMN morphology allows flexibility for diapedesis into tissues.
Option Analysis
| Option | Description | PMN Leucocytes? |
|---|---|---|
| (1) Macrophages | Large mononuclear phagocytes derived from monocytes; single kidney-shaped nucleus, no granules [web: prior biology context]. | No |
| (2) Neutrophils | Granulocytes with polymorphic (multi-lobed) nuclei; most abundant PMNs for bacterial killing. | Yes |
| (3) Monocytes | Circulating mononuclear precursors to macrophages/dendritic cells; horseshoe-shaped nucleus. | No |
| (4) Eosinophils | Granulocytes with bi-lobed nuclei targeting parasites/allergies; also PMNs but question specifies primary/common PMNs as neutrophils. | Partially, but not primary |
Clinical Relevance
PMNs, especially neutrophils, dominate pus in infections; elevated counts (neutrophilia) signal bacterial issues. Understanding PMN vs. mononuclear cells aids differential WBC counts in diagnostics for molecular biology, microbiology studies.
