Gastrointestinal: secretory IgA transport: 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 · Gastrointestinal: secretory IgA transport

Sample item

A newborn is protected against gut infections by antibody in breast milk. Which cell process delivers dimeric IgA across the mammary epithelium into the milk?

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

The answer and the reasoning

A. Transcytosis using the polymeric immunoglobulin receptor

Dimeric IgA bound by J chain binds the poly-Ig receptor on the basolateral surface, is carried across by transcytosis, and is released with a secretory component that protects it from proteases.

Option by option

  • A. Transcytosis using the polymeric immunoglobulin receptor (correct)

    Correct. The poly-Ig receptor transports dimeric IgA by transcytosis.

  • B. Active secretion by the Na-K ATPase

    The Na-K ATPase moves ions and not immunoglobulins.

  • C. Pinocytosis by macrophages

    Macrophage pinocytosis does not deliver antibodies into milk.

  • D. Passive diffusion through tight junctions

    Tight junctions exclude large proteins like 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 Physiology question

What is the answer to this Physiology question?

The best answer is A, Transcytosis using the polymeric immunoglobulin receptor. Dimeric IgA bound by J chain binds the poly-Ig receptor on the basolateral surface, is carried across by transcytosis, and is released with a secretory component that protects it from proteases.

Why is "Active secretion by the Na-K ATPase" not the answer?

The Na-K ATPase moves ions and not immunoglobulins.

Why is "Pinocytosis by macrophages" not the answer?

Macrophage pinocytosis does not deliver antibodies into milk.

Why is "Passive diffusion through tight junctions" not the answer?

Tight junctions exclude large proteins like antibody.

What concept does this question test?

It tests Gastrointestinal: secretory IgA transport in Physiology. The correct option holds because: Correct. The poly-Ig receptor transports dimeric IgA by transcytosis.

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 Gastrointestinal: secretory IgA transport?

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.