Immunology: complement deficiency: 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: complement deficiency

Sample item

Recurrent invasive infections with Neisseria species should prompt evaluation for deficiency of which complement components?

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

The answer and the reasoning

D. C5 through C9

Terminal complement components form the membrane attack complex, which is particularly important for killing Neisseria. C5-C9 deficiency predisposes to recurrent meningococcal and gonococcal infection.

Option by option

  • A. C1 esterase inhibitor

    C1 esterase inhibitor deficiency causes hereditary angioedema.

  • B. C3 only

    C3 deficiency causes broad susceptibility to encapsulated bacteria, not the classic isolated Neisseria pattern.

  • C. Mannose-binding lectin only

    Mannose-binding lectin deficiency has a less specific, usually milder pattern.

  • D. C5 through C9 (correct)

    Correct. Terminal-pathway deficiency impairs membrane attack complex formation.

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 Microbiology question

What is the answer to this Microbiology question?

The best answer is D, C5 through C9. Terminal complement components form the membrane attack complex, which is particularly important for killing Neisseria.

Why is "C1 esterase inhibitor" not the answer?

C1 esterase inhibitor deficiency causes hereditary angioedema.

Why is "C3 only" not the answer?

C3 deficiency causes broad susceptibility to encapsulated bacteria, not the classic isolated Neisseria pattern.

Why is "Mannose-binding lectin only" not the answer?

Mannose-binding lectin deficiency has a less specific, usually milder pattern.

What concept does this question test?

It tests Immunology: complement deficiency in Microbiology. C5-C9 deficiency predisposes to recurrent meningococcal and gonococcal infection.

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: complement deficiency?

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.