Which complement component, generated during acute inflammation, directly causes mast cell degranulation and increased vascular permeability without requiring immune complex formation?

• A C3b
• B C4b
• C C1q
• D C5a ✓

Explanation

C5a (anaphylatoxin) is the most potent complement-derived mediator: it directly triggers mast cell degranulation (releasing histamine and leukotrienes), causes smooth muscle contraction, and is a powerful chemotactic agent for neutrophils. C3a is also an anaphylatoxin but less potent. C3b is primarily an opsonin; C1q initiates the classical pathway; C4b also functions as an opsonin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.