Immunopathology: 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

Sample item

A man is given horse-derived antivenom after a snakebite. Eight days later he develops fever, urticarial rash and painful joints, and serum C3 is low. Which type of hypersensitivity explains this picture?

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

The answer and the reasoning

C. Type III, immune complex mediated

Serum sickness follows exposure to a large dose of foreign protein, with antibodies forming about a week later and combining with circulating antigen. The complexes deposit in joints, skin and vessels, activate complement and consume C3.

Option by option

  • A. Type I, IgE mediated

    Type I reactions occur within minutes of re-exposure, with anaphylaxis or urticaria, and do not lower complement.

  • B. Type IV, delayed T cell mediated

    Type IV reactions are mediated by T cells over 48 to 72 hours, as in the tuberculin test, and do not depend on complement consumption.

  • C. Type III, immune complex mediated (correct)

    Correct. Circulating antigen-antibody complexes deposit in tissues and consume complement after a delay of about a week.

  • D. Type II, antibody mediated against cell surface antigens

    Type II reactions involve antibody binding fixed cell or matrix antigens, as in haemolytic anaemia or Goodpasture disease.

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 Pathology questions

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is C, Type III, immune complex mediated. Serum sickness follows exposure to a large dose of foreign protein, with antibodies forming about a week later and combining with circulating antigen.

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

Type I reactions occur within minutes of re-exposure, with anaphylaxis or urticaria, and do not lower complement.

Why is "Type IV, delayed T cell mediated" not the answer?

Type IV reactions are mediated by T cells over 48 to 72 hours, as in the tuberculin test, and do not depend on complement consumption.

Why is "Type II, antibody mediated against cell surface antigens" not the answer?

Type II reactions involve antibody binding fixed cell or matrix antigens, as in haemolytic anaemia or Goodpasture disease.

What concept does this question test?

It tests Immunopathology in Pathology. The complexes deposit in joints, skin and vessels, activate complement and consume C3.

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 Immunopathology?

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.