Blood and immunity: lymphocyte homing: practice question

A Physiology 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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Physiology · Blood and immunity: lymphocyte homing

Sample item

Naive lymphocytes continually leave the blood and enter lymph nodes. Through which structure and with which adhesion molecule do they cross?

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

The answer and the reasoning

C. High endothelial venules, using L-selectin

Naive lymphocytes roll on high endothelial venules of the paracortex through L-selectin binding to sialylated ligands such as GlyCAM-1 and CD34. Chemokines then activate integrins for firm adhesion and transmigration. Afferent lymphatics carry antigen-presenting cells into the node.

Option by option

  • A. Splenic red pulp sinusoids, using integrins on the sinus wall

    Splenic sinusoids are a feature of the spleen, not lymph node entry.

  • B. Afferent lymphatics, using ICAM-1

    Afferent lymphatics bring lymph and dendritic cells into the node, not blood-borne lymphocytes.

  • C. High endothelial venules, using L-selectin (correct)

    Correct. L-selectin on naive lymphocytes binds ligands on high endothelial venules.

  • D. Medullary sinuses, using CD4

    Medullary sinuses drain lymph out of the node, and CD4 is a T-cell co-receptor, not an adhesion molecule for entry.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, High endothelial venules, using L-selectin. Naive lymphocytes roll on high endothelial venules of the paracortex through L-selectin binding to sialylated ligands such as GlyCAM-1 and CD34.

Why is "Splenic red pulp sinusoids, using integrins on the sinus wall" not the answer?

Splenic sinusoids are a feature of the spleen, not lymph node entry.

Why is "Afferent lymphatics, using ICAM-1" not the answer?

Afferent lymphatics bring lymph and dendritic cells into the node, not blood-borne lymphocytes.

Why is "Medullary sinuses, using CD4" not the answer?

Medullary sinuses drain lymph out of the node, and CD4 is a T-cell co-receptor, not an adhesion molecule for entry.

What concept does this question test?

It tests Blood and immunity: lymphocyte homing in Physiology. Chemokines then activate integrins for firm adhesion and transmigration. Afferent lymphatics carry antigen-presenting cells into the node.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Blood and immunity: lymphocyte homing?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.