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Question 336
Physiology → Haematology
Classification
Question
SSBAQuestion Header
Activated lymphocytes release a factor that increases proliferation of monocyte stem cells in bone marrow. Which combination correctly identifies the lymphocyte and mediator involved?
Question Stem
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Options
A
B lymphocyte — histamine
B
B lymphocyte — serotonin
C
T lymphocyte — factor XIII
D
T lymphocyte — GM-CSF
E
T lymphocyte — heparin
Explanation
Activated T lymphocytes release granulocyte/macrophage colony-stimulating factor (GM-CSF), which stimulates monocyte stem cells to proliferate. Monocyte numbers can therefore increase when their parent cells are stimulated by factors released from activated lymphocytes.
Option Validity
A) Histamine is characteristic of basophil granules and is not the mediator responsible for stimulation of monocyte stem-cell proliferation.
B) Serotonin is found in platelet dense granules and does not represent the T-cell signal described for monocyte production.
C) Factor XIII participates in stabilisation of the fibrin clot rather than stimulation of monocyte stem cells.
E) Heparin is present in basophil granules and is not the T-lymphocyte mediator responsible for monocyte stem-cell proliferation.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 3: Physiology – Haematology. pp.69–70.