During leukocyte margination and rolling along postcapillary venular endothelium, the initial tethering interaction involves binding of endothelial selectins to their counter-receptor on leukocytes. What is this leukocyte counter-receptor?

• A Sialyl-Lewis X modified glycoprotein ✓
• B Integrin LFA-1 (CD11a/CD18)
• C PECAM-1 (CD31)
• D ICAM-1

Explanation

Rolling is mediated by selectins, which are calcium-dependent lectins that recognize specific carbohydrate structures. On leukocytes, the relevant structure is the sialyl-Lewis X modified glycoprotein, which binds E-selectin and P-selectin on activated endothelium. ICAM-1 and PECAM-1 participate in later steps: ICAM-1 engages integrins during firm adhesion, and PECAM-1 mediates transmigration through interendothelial junctions, not the initial carbohydrate-dependent rolling event.

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.