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Pathology · Inflammation and repair: pentraxins
Sample itemA patient with bacterial pneumonia shows markedly raised C-reactive protein. How does this acute phase protein help host defence?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
D. Binds bacterial phosphocholine and activates complement as an opsonin
CRP is a pentraxin that binds phosphocholine on microbial surfaces and damaged cells, activating the classical complement pathway and acting as an opsonin. Its rapid rise makes it a useful marker of inflammation.
Option by option
A. Neutralises superoxide anions in tissue
Superoxide neutralisation is done by superoxide dismutase.
B. Cross-links fibrin to stabilise clots
Fibrin cross-linking is the role of factor XIII.
C. Binds free iron to reduce its availability to microbes
Iron binding in inflammation is by lactoferrin and hepcidin-driven sequestration, not CRP.
D. Binds bacterial phosphocholine and activates complement as an opsonin (correct)
Correct. CRP binds microbial phosphocholine, opsonises and fixes complement.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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