Immunopathology: hypersensitivity types: practice question

A Pathology 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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Pathology · Immunopathology: hypersensitivity types

Sample item

A farmer develops cough and dyspnoea 6 hours after cleaning a mouldy hay store. His serum has precipitating IgG against thermophilic actinomycetes. Which hypersensitivity mechanism is dominant at this stage?

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

The answer and the reasoning

C. Type III immune complex reaction

Acute hypersensitivity pneumonitis, such as farmer's lung, is mostly an immune complex (type III) reaction occurring hours after exposure. The chronic form has type IV T-cell mediated granulomas.

Option by option

  • A. Type IV delayed reaction with granulomas only

    Type IV reactions take 24 to 72 hours, and granulomas mark the chronic phase.

  • B. Type II antibody-mediated cytotoxicity

    Type II reactions involve antibody against cell surface antigens, as in transfusion reactions.

  • C. Type III immune complex reaction (correct)

    Correct. Precipitating IgG and a reaction at 4 to 8 hours indicate an Arthus-type immune complex reaction.

  • D. Type I IgE mediated degranulation

    Type I reactions appear within minutes and involve IgE, with wheeze and urticaria.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Type III immune complex reaction. Acute hypersensitivity pneumonitis, such as farmer's lung, is mostly an immune complex (type III) reaction occurring hours after exposure.

Why is "Type IV delayed reaction with granulomas only" not the answer?

Type IV reactions take 24 to 72 hours, and granulomas mark the chronic phase.

Why is "Type II antibody-mediated cytotoxicity" not the answer?

Type II reactions involve antibody against cell surface antigens, as in transfusion reactions.

Why is "Type I IgE mediated degranulation" not the answer?

Type I reactions appear within minutes and involve IgE, with wheeze and urticaria.

What concept does this question test?

It tests Immunopathology: hypersensitivity types in Pathology. The chronic form has type IV T-cell mediated granulomas.

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 Immunopathology: hypersensitivity types?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.