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Question 306
Physiology → Haematology
Classification
Question
SSBAQuestion Header
A granulocyte has a bilobed spectacle-shaped nucleus and coarse granules staining pink-red with eosin. Which additional property best matches this cell?
Question Stem
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Options
A
It contains histamine and heparin as its defining granule contents
B
It normally accounts for 60-70% of circulating leucocytes
C
It is associated with defence against parasites and allergic responses
D
It migrates into tissues and becomes a macrophage
E
It mediates humoral immunity by producing immunoglobulins
Explanation
The morphology identifies an eosinophil. Eosinophils comprise approximately 1–4% of white cells, have coarse pink-red eosin-staining granules and a bilobed nucleus, and are associated with parasitic infestation, allergy and mucosal immunity.
Option Validity
A) Histamine and heparin are characteristic contents of basophil granules. The morphology in the stem instead identifies an eosinophil.
B) Approximately 60–70% of circulating leucocytes are neutrophils. Eosinophils constitute a much smaller proportion.
D) Migration into tissues followed by differentiation into macrophages is the fate of monocytes. It is not the characteristic fate of eosinophils.
E) Humoral immunity and immunoglobulin production are associated with B lymphocytes. Eosinophils are instead linked to parasites, allergy and mucosal immunity.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Eosinophils, p.69.