Immunology: IgA1 protease: 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: IgA1 protease

Sample item

Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae can all colonise the nasopharynx despite mucosal antibody. Which shared virulence factor helps them evade this defence by cleaving the hinge region of the predominant mucosal immunoglobulin subclass?

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

The answer and the reasoning

C. IgA1 protease

These mucosal pathogens secrete IgA1-specific proteases that cut the hinge region, releasing Fab fragments and impairing agglutination and blocking of adherence. This helps colonisation of mucosal surfaces. Protein A, M protein and coagulase act through other mechanisms.

Option by option

  • A. M protein

    M protein of group A streptococci resists phagocytosis, and it is not a protease.

  • B. Coagulase

    Coagulase converts fibrinogen to fibrin and forms a protective clot around staphylococci.

  • C. IgA1 protease (correct)

    Correct. IgA1 protease cleaves the hinge of IgA1, disabling mucosal antibody.

  • D. Protein A

    Protein A of Staphylococcus aureus binds the Fc portion of IgG and impairs opsonisation, but it does not cleave IgA.

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, IgA1 protease. These mucosal pathogens secrete IgA1-specific proteases that cut the hinge region, releasing Fab fragments and impairing agglutination and blocking of adherence.

Why is "M protein" not the answer?

M protein of group A streptococci resists phagocytosis, and it is not a protease.

Why is "Coagulase" not the answer?

Coagulase converts fibrinogen to fibrin and forms a protective clot around staphylococci.

Why is "Protein A" not the answer?

Protein A of Staphylococcus aureus binds the Fc portion of IgG and impairs opsonisation, but it does not cleave IgA.

What concept does this question test?

It tests Immunology: IgA1 protease in Microbiology. This helps colonisation of mucosal surfaces. Protein A, M protein and coagulase act through other mechanisms.

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: IgA1 protease?

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.