Immunology: 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

Sample item

A young adult is admitted with his second episode of meningococcal meningitis. Which immune defect should be suspected?

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

The answer and the reasoning

C. Deficiency of a terminal complement component (C5 to C9)

The terminal components C5 to C9 form the membrane attack complex, which is especially important for killing Neisseria. Their deficiency predisposes to recurrent, often unusual, meningococcal or gonococcal disease.

Option by option

  • A. Deficiency of the early component C4

    Early component deficiencies such as C4 are associated with immune complex disease like lupus.

  • B. Deficiency of CD59 and DAF

    CD59 and DAF deficiency causes complement-mediated lysis of red cells in paroxysmal nocturnal haemoglobinuria.

  • C. Deficiency of a terminal complement component (C5 to C9) (correct)

    Correct. Lack of the membrane attack complex impairs killing of Neisseria.

  • D. C1 esterase inhibitor deficiency

    C1 esterase inhibitor deficiency causes hereditary angioedema, not recurrent Neisseria infection.

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, Deficiency of a terminal complement component (C5 to C9). The terminal components C5 to C9 form the membrane attack complex, which is especially important for killing Neisseria.

Why is "Deficiency of the early component C4" not the answer?

Early component deficiencies such as C4 are associated with immune complex disease like lupus.

Why is "Deficiency of CD59 and DAF" not the answer?

CD59 and DAF deficiency causes complement-mediated lysis of red cells in paroxysmal nocturnal haemoglobinuria.

Why is "C1 esterase inhibitor deficiency" not the answer?

C1 esterase inhibitor deficiency causes hereditary angioedema, not recurrent Neisseria infection.

What concept does this question test?

It tests Immunology in Microbiology. Their deficiency predisposes to recurrent, often unusual, meningococcal or gonococcal disease.

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?

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.