Question

Leukocyte migration through endothelium is induced by -

• A. Selectin
• B. N CAM
• C. C CAM
• D. PECAM

Hint:

Transmigration (diapedesis) is mediated by PECAM-1 (CD31).

Answer 1

The Correct Option is D

Step 1: Picture the recruitment sequence. To leave a vessel a white cell first rolls, then sticks firmly, then crawls between two endothelial cells into the tissue. That last crawling step through the junction is diapedesis, and it happens chiefly in postcapillary venules.

Step 2: Pin the junctional molecule. The protein that lines the endothelial cell-to-cell junction and lets the leukocyte pass is PECAM-1, also tagged CD31, a member of the immunoglobulin superfamily. Its presence on both the leukocyte and the junction is what guides transmigration. Hence the answer is PECAM.

Step 3: Avoid mixing up the phases. Selectins are the rolling molecules and integrins with their ICAM/VCAM partners give firm adhesion; neither performs the final passage through the wall.

Step 4: Dismiss the rest. N-CAM operates in nervous tissue and C-CAM is not the diapedesis molecule, so they do not fit.

\[\boxed{\text{PECAM}}\]