Inflammation and repair: PECAM-1 and transmigration: practice question

A Pathology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pathology · Inflammation and repair: PECAM-1 and transmigration

Sample item

After firm adhesion to the endothelium, leukocytes squeeze between endothelial cells in postcapillary venules to enter the tissue. Which molecule on both leukocytes and endothelium chiefly mediates this transmigration?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. PECAM-1 (CD31)

Diapedesis occurs mainly at intercellular junctions and is mediated by PECAM-1 (CD31), expressed on leukocytes and endothelial cells, along with other junctional molecules. Rolling depends on selectins and their ligands, and firm adhesion on integrins binding ICAM-1. After crossing the endothelium, leukocytes penetrate the basement membrane by secreting collagenases.

Option by option

  • A. Sialyl Lewis X

    Sialyl Lewis X is the leukocyte ligand for selectins during rolling.

  • B. ICAM-1

    ICAM-1 binds leukocyte integrins to produce firm adhesion.

  • C. L-selectin

    L-selectin on leukocytes takes part in rolling, an earlier step.

  • D. PECAM-1 (CD31) (correct)

    Correct. PECAM-1 on both cell types guides the leukocyte through the endothelial junction.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is D, PECAM-1 (CD31). Diapedesis occurs mainly at intercellular junctions and is mediated by PECAM-1 (CD31), expressed on leukocytes and endothelial cells, along with other junctional molecules.

Why is "Sialyl Lewis X" not the answer?

Sialyl Lewis X is the leukocyte ligand for selectins during rolling.

Why is "ICAM-1" not the answer?

ICAM-1 binds leukocyte integrins to produce firm adhesion.

Why is "L-selectin" not the answer?

L-selectin on leukocytes takes part in rolling, an earlier step.

What concept does this question test?

It tests Inflammation and repair: PECAM-1 and transmigration in Pathology. Rolling depends on selectins and their ligands, and firm adhesion on integrins binding ICAM-1. After crossing the endothelium, leukocytes penetrate the basement membrane by secreting collagenases.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Inflammation and repair: PECAM-1 and transmigration?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.