During neutrophil transmigration in acute inflammation, which molecular interaction mediates firm adhesion (the step following initial rolling) to endothelium?

• A L-selectin on neutrophils binding GlyCAM-1 on endothelium
• B Beta-2 integrin (LFA-1/Mac-1) binding to ICAM-1 on activated endothelium ✓
• C PECAM-1 (CD31) diapedesis across junctions
• D P-selectin binding to PSGL-1 on neutrophils

Explanation

Firm adhesion (sticking) of neutrophils to endothelium requires integrin activation: chemokines presented on the endothelial surface activate neutrophil beta-2 integrins (LFA-1/CD11a-CD18 and Mac-1/CD11b-CD18) via inside-out signaling, switching them to high-affinity conformations that tightly bind ICAM-1 and ICAM-2 on cytokine-activated endothelium. P-selectin/PSGL-1 and E-selectin interactions mediate the earlier rolling step. PECAM-1 mediates the final diapedesis (transmigration) through junctions.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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