Which complement fragment is the most potent anaphylatoxin, stimulating histamine release from mast cells and increasing vascular permeability during acute inflammation?
- A C5a ✓
- B C3b
- C C3a
- D C4a
Correct answer: A. C5a
Explanation
A5a is the most potent anaphylatoxin; it triggers mast cell degranulation, increases vascular permeability, is a strong chemoattractant for neutrophils and monocytes, and activates the lipoxygenase pathway. A3a and A4a are also anaphylatoxins but far weaker. A3b is an opsonin that coats particles for phagocytosis via complement receptors and has no mast cell degranulating activity, which kills the most tempting distractor.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.