Immunology: molecular mimicry: 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: molecular mimicry

Sample item

A 30-year-old man develops ascending flaccid paralysis two weeks after an episode of Campylobacter jejuni gastroenteritis. Antibodies raised against bacterial lipo-oligosaccharide cross-react with peripheral nerve gangliosides. Which mechanism of autoimmunity is illustrated?

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

The answer and the reasoning

C. Molecular mimicry

In molecular mimicry, an immune response to a microbial antigen cross-reacts with a structurally similar self antigen, here ganglioside epitopes on peripheral nerves, causing Guillain-Barre syndrome. Rheumatic fever following group A streptococcal infection is another example. The immune response is initially appropriate but targets self.

Option by option

  • A. Release of sequestered antigen

    Release of sequestered antigen describes exposure of hidden antigens such as lens or testicular proteins after injury.

  • B. Polyclonal B cell activation by a superantigen

    Superantigen-driven polyclonal activation is not the mechanism for this antigen-specific cross-reaction.

  • C. Molecular mimicry (correct)

    Correct. Shared epitopes between the organism and nerve gangliosides cause cross-reactive autoantibodies.

  • D. Loss of central tolerance due to AIRE deficiency

    AIRE deficiency causes a polyendocrine syndrome, not post-infectious neuropathy.

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.

More Microbiology questions

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Molecular mimicry. In molecular mimicry, an immune response to a microbial antigen cross-reacts with a structurally similar self antigen, here ganglioside epitopes on peripheral nerves, causing Guillain-Barre syndrome.

Why is "Release of sequestered antigen" not the answer?

Release of sequestered antigen describes exposure of hidden antigens such as lens or testicular proteins after injury.

Why is "Polyclonal B cell activation by a superantigen" not the answer?

Superantigen-driven polyclonal activation is not the mechanism for this antigen-specific cross-reaction.

Why is "Loss of central tolerance due to AIRE deficiency" not the answer?

AIRE deficiency causes a polyendocrine syndrome, not post-infectious neuropathy.

What concept does this question test?

It tests Immunology: molecular mimicry in Microbiology. Rheumatic fever following group A streptococcal infection is another example. The immune response is initially appropriate but targets self.

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: molecular mimicry?

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.