Which of the following complement components function as anaphylatoxins, causing mast cell degranulation and smooth muscle contraction?

• A C3a, C5a, and C4a ✓
• B C2a and C4a
• C C5b, C6, and C7
• D C3b and iC3b

Explanation

C3a, C5a, and C4a bind receptors on mast cells and basophils and trigger degranulation with histamine release, producing vasodilation and increased vascular permeability. C5a is also a potent neutrophil chemoattractant and activator. The options in C are late complement components that form the membrane attack complex, while C3b and iC3b are opsonins that coat particles for phagocytosis, so neither pair has anaphylatoxin activity.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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