Immunology: antigen processing: 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: antigen processing

Sample item

A patient has an inherited deficiency of TAP1 transporter. Which immune function is most directly impaired?

AImmunoglobulin class switch recombinationBPresentation of cytosolic peptides on MHC class I to CD8 T cellsCFormation of the C3 convertaseDPresentation of phagocytosed antigens on MHC class II to CD4 T cells

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

The answer and the reasoning

B. Presentation of cytosolic peptides on MHC class I to CD8 T cells

Endogenous antigens are degraded by the proteasome, and TAP transports the peptides into the endoplasmic reticulum, where they are loaded onto MHC class I. TAP deficiency (a form of bare lymphocyte syndrome) leaves class I molecules unstable and poorly expressed, impairing CD8 T cell responses.

Option by option

A. Immunoglobulin class switch recombination
Class switching depends on CD40L and AID, not TAP.
B. Presentation of cytosolic peptides on MHC class I to CD8 T cells (correct)
Correct. TAP supplies the peptides that stabilise MHC class I.
C. Formation of the C3 convertase
C3 convertase formation depends on complement proteins, not antigen processing.
D. Presentation of phagocytosed antigens on MHC class II to CD4 T cells
Class II presentation uses endosomal degradation and invariant chain, independent of TAP.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Presentation of cytosolic peptides on MHC class I to CD8 T cells. Endogenous antigens are degraded by the proteasome, and TAP transports the peptides into the endoplasmic reticulum, where they are loaded onto MHC class I.

Why is "Immunoglobulin class switch recombination" not the answer?

Class switching depends on CD40L and AID, not TAP.

Why is "Formation of the C3 convertase" not the answer?

C3 convertase formation depends on complement proteins, not antigen processing.

Why is "Presentation of phagocytosed antigens on MHC class II to CD4 T cells" not the answer?

Class II presentation uses endosomal degradation and invariant chain, independent of TAP.

What concept does this question test?

It tests Immunology: antigen processing in Microbiology. TAP deficiency (a form of bare lymphocyte syndrome) leaves class I molecules unstable and poorly expressed, impairing CD8 T cell responses.

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 Immunology: antigen processing?

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.