Inflammation: leukocyte extravasation: 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: leukocyte extravasation

Sample item

A patient with relapsing multiple sclerosis receives natalizumab, a monoclonal antibody against the alpha-4 integrin subunit. Which step in leukocyte extravasation is primarily impaired?

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

The answer and the reasoning

D. Firm adhesion of leukocytes to endothelium through VCAM-1

Rolling is mediated by selectins, firm adhesion by leukocyte integrins binding endothelial ligands such as ICAM-1 and VCAM-1, and diapedesis by PECAM-1 (CD31). The alpha-4 integrin VLA-4 on lymphocytes binds VCAM-1, so blocking it stops lymphocytes from entering the central nervous system. A recognised adverse effect of natalizumab is progressive multifocal leukoencephalopathy.

Option by option

  • A. Chemotaxis of leukocytes toward complement fragment C5a

    Chemotaxis is driven by chemokines and C5a, and does not depend on alpha-4 integrin.

  • B. Rolling of leukocytes along the endothelium through selectins

    Rolling depends on P-selectin and E-selectin on endothelium and sialyl Lewis X on leukocytes, not on alpha-4 integrin.

  • C. Transmigration between endothelial cells through PECAM-1

    Transmigration uses PECAM-1 on both leukocytes and endothelium, which is not the target here.

  • D. Firm adhesion of leukocytes to endothelium through VCAM-1 (correct)

    Correct. The alpha-4 integrin and VCAM-1 interaction anchors the cell and is blocked by the antibody.

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, Firm adhesion of leukocytes to endothelium through VCAM-1. Rolling is mediated by selectins, firm adhesion by leukocyte integrins binding endothelial ligands such as ICAM-1 and VCAM-1, and diapedesis by PECAM-1 (CD31).

Why is "Chemotaxis of leukocytes toward complement fragment C5a" not the answer?

Chemotaxis is driven by chemokines and C5a, and does not depend on alpha-4 integrin.

Why is "Rolling of leukocytes along the endothelium through selectins" not the answer?

Rolling depends on P-selectin and E-selectin on endothelium and sialyl Lewis X on leukocytes, not on alpha-4 integrin.

Why is "Transmigration between endothelial cells through PECAM-1" not the answer?

Transmigration uses PECAM-1 on both leukocytes and endothelium, which is not the target here.

What concept does this question test?

It tests Inflammation: leukocyte extravasation in Pathology. The alpha-4 integrin VLA-4 on lymphocytes binds VCAM-1, so blocking it stops lymphocytes from entering the central nervous system. A recognised adverse effect of natalizumab is progressive multifocal leukoencephalopathy.

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: leukocyte extravasation?

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.