Immunology: cross-presentation: 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: cross-presentation

Sample item

A virus infects only airway epithelial cells and does not infect dendritic cells, yet naive CD8 T cells in the draining node are primed against viral peptides. Which mechanism allows this?

AB cells present viral peptides to CD8 T cells on MHC class IIBThe virus acts as a superantigen for CD8 T cellsCEpithelial cells present viral peptides on MHC class II to CD8 T cellsDDendritic cells take up infected cell debris and present its antigens on MHC class I

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

The answer and the reasoning

D. Dendritic cells take up infected cell debris and present its antigens on MHC class I

Specialised dendritic cells can capture exogenous antigen from dead or infected cells and route it into the MHC class I pathway, a process called cross-presentation. This primes CD8 cytotoxic T cells against viruses and tumours that do not infect antigen-presenting cells. Classically, exogenous antigen is presented on MHC class II to CD4 cells.

Option by option

A. B cells present viral peptides to CD8 T cells on MHC class II
B cells present on MHC class II to CD4 T cells and do not prime naive CD8 cells in this way.
B. The virus acts as a superantigen for CD8 T cells
Superantigens bridge MHC class II and the T cell receptor beta chain, and they are not required for CD8 priming.
C. Epithelial cells present viral peptides on MHC class II to CD8 T cells
CD8 T cells are restricted by MHC class I, not class II.
D. Dendritic cells take up infected cell debris and present its antigens on MHC class I (correct)
Correct. Cross-presentation lets dendritic cells display exogenous antigen on MHC class I to naive CD8 T cells.

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 D, Dendritic cells take up infected cell debris and present its antigens on MHC class I. Specialised dendritic cells can capture exogenous antigen from dead or infected cells and route it into the MHC class I pathway, a process called cross-presentation.

Why is "B cells present viral peptides to CD8 T cells on MHC class II" not the answer?

B cells present on MHC class II to CD4 T cells and do not prime naive CD8 cells in this way.

Why is "The virus acts as a superantigen for CD8 T cells" not the answer?

Superantigens bridge MHC class II and the T cell receptor beta chain, and they are not required for CD8 priming.

Why is "Epithelial cells present viral peptides on MHC class II to CD8 T cells" not the answer?

CD8 T cells are restricted by MHC class I, not class II.

What concept does this question test?

It tests Immunology: cross-presentation in Microbiology. This primes CD8 cytotoxic T cells against viruses and tumours that do not infect antigen-presenting cells. Classically, exogenous antigen is presented on MHC class II to CD4 cells.

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: cross-presentation?

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.