A 30-year-old man has a localized abscess. The neutrophil accumulation in this abscess is driven by directional migration toward chemokines. Which complement fragment is the MOST potent chemotactic agent for neutrophils?

• A C3a
• B C4b
• C C1q
• D C5a ✓

Explanation

C5a is a potent chemotactic agent and anaphylatoxin that attracts neutrophils and monocytes along concentration gradients. It also increases vascular permeability and activates mast cells. C3a is an anaphylatoxin but weaker as a chemotactic agent for neutrophils. C4b is an opsonin rather than a chemotactic factor.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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