Immunology: secretory IgA: practice question

A Microbiology 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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Microbiology · Immunology: secretory IgA

Sample item

Which feature explains why secretory IgA remains intact in the protease-rich lumen of the gut?

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

The answer and the reasoning

B. Association with the secretory component

Secretory IgA is a dimer joined by a J chain and wrapped in the secretory component, acquired during transcytosis through the epithelium, which protects it from proteases. Pentameric structure belongs to IgM, and C1q binding is a feature of IgM and IgG.

Option by option

  • A. Binding to complement C1q

    C1q binding does not protect IgA from proteases and is not a feature of IgA.

  • B. Association with the secretory component (correct)

    Correct. The secretory component protects IgA from degradation.

  • C. A pentameric structure with J chain

    The pentamer with J chain describes IgM.

  • D. Presence of an Fc receptor for neonatal transfer

    Neonatal Fc receptor transfers IgG across the placenta, not IgA protection.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Association with the secretory component. Secretory IgA is a dimer joined by a J chain and wrapped in the secretory component, acquired during transcytosis through the epithelium, which protects it from proteases.

Why is "Binding to complement C1q" not the answer?

C1q binding does not protect IgA from proteases and is not a feature of IgA.

Why is "A pentameric structure with J chain" not the answer?

The pentamer with J chain describes IgM.

Why is "Presence of an Fc receptor for neonatal transfer" not the answer?

Neonatal Fc receptor transfers IgG across the placenta, not IgA protection.

What concept does this question test?

It tests Immunology: secretory IgA in Microbiology. Pentameric structure belongs to IgM, and C1q binding is a feature of IgM and IgG.

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 Immunology: secretory IgA?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology 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.