Q.68 Which one of the following leukocytes are present in the largest proportion in
healthy human blood?
(A) Neutrophils
(B) Eosinophils
(C) Basophiles
(D) Monocytes
Neutrophils constitute the largest proportion of leukocytes in healthy human blood. This multiple-choice question tests knowledge of the differential white blood cell (WBC) count, a key concept in hematology relevant for exams like CSIR NET Life Sciences.
Option Analysis
Neutrophils (A): These granulocytes make up 40-75% of total WBCs, serving as the first line of defense against bacterial infections through phagocytosis. In healthy adults, they dominate the differential count at around 50-70%.
Eosinophils (B): These account for only 1-6% of WBCs, primarily combating parasitic infections and modulating allergic responses.
Basophils (C): The rarest type at 0.5-1%, basophils release histamine and heparin during allergic reactions and inflammation.
Monocytes (D): Comprising 2-10% of WBCs, monocytes differentiate into macrophages to engulf pathogens and debris.
Correct Answer
The answer is (A) Neutrophils, as confirmed by standard reference ranges across medical sources.
Introduction
In healthy human blood, leukocytes (white blood cells) maintain immune balance, with neutrophils present in the largest proportion at 40-75% of the total differential count. This key fact helps diagnose infections and is crucial for competitive exams like CSIR NET Life Sciences, where questions on leukocyte proportions test hematology knowledge. Understanding the largest proportion of leukocytes ensures mastery of blood composition basics.
Leukocyte Types and Percentages
Healthy human blood contains five main leukocytes, measured via differential WBC count:
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Neutrophils: 40-75% – Phagocytose bacteria; most abundant.
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Lymphocytes: 20-40% – Drive adaptive immunity.
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Monocytes: 2-10% – Become tissue macrophages.
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Eosinophils: 1-6% – Target parasites and allergies.
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Basophils: 0.5-1% – Least common; release histamines.
These proportions reflect a total WBC count of 4,000-11,000 per microliter.
Functions in Immune Defense
Neutrophils, the dominant leukocytes, form pus at infection sites and release antimicrobial nets. Eosinophils and basophils handle allergies/parasites, while monocytes clear debris—none rival neutrophils’ prevalence in healthy blood.
Clinical Relevance for Exams
Elevated neutrophils signal bacterial issues; declines indicate immunosuppression. CSIR NET questions often feature this descending order: neutrophils > lymphocytes > monocytes > eosinophils > basophils. Track via complete blood count (CBC) tests.
