Immunology: eosinophil-mediated killing of helminths: 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: eosinophil-mediated killing of helminths

Sample item

Schistosomula are far too large to be phagocytosed. Which mechanism allows the host to damage them?

ANeutrophils ingest the larvae after IgM opsonisationBCytotoxic CD8 T cells kill them by perforinCEosinophils bind IgE coating the parasite and release major basic proteinDComplement membrane attack complex alone lyses the tegument

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

The answer and the reasoning

C. Eosinophils bind IgE coating the parasite and release major basic protein

Helminths are killed by antibody-dependent cell-mediated cytotoxicity. IgE bound to the parasite surface is recognised by Fc epsilon receptors on eosinophils, which degranulate, releasing major basic protein and other toxic granule contents. This explains eosinophilia and raised IgE in helminth infection.

Option by option

A. Neutrophils ingest the larvae after IgM opsonisation
Neutrophils cannot ingest an organism of this size, and IgM is not the main antibody in this defence.
B. Cytotoxic CD8 T cells kill them by perforin
CD8 T cells kill virus-infected or tumour cells presenting peptide on MHC class I, not extracellular helminths.
C. Eosinophils bind IgE coating the parasite and release major basic protein (correct)
Correct. IgE-dependent eosinophil degranulation damages large parasites.
D. Complement membrane attack complex alone lyses the tegument
Complement alone is not the main defence, as schistosomula develop resistance to complement-mediated lysis.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Eosinophils bind IgE coating the parasite and release major basic protein. Helminths are killed by antibody-dependent cell-mediated cytotoxicity.

Why is "Neutrophils ingest the larvae after IgM opsonisation" not the answer?

Neutrophils cannot ingest an organism of this size, and IgM is not the main antibody in this defence.

Why is "Cytotoxic CD8 T cells kill them by perforin" not the answer?

CD8 T cells kill virus-infected or tumour cells presenting peptide on MHC class I, not extracellular helminths.

Why is "Complement membrane attack complex alone lyses the tegument" not the answer?

Complement alone is not the main defence, as schistosomula develop resistance to complement-mediated lysis.

What concept does this question test?

It tests Immunology: eosinophil-mediated killing of helminths in Microbiology. IgE bound to the parasite surface is recognised by Fc epsilon receptors on eosinophils, which degranulate, releasing major basic protein and other toxic granule contents. This explains eosinophilia and raised IgE in helminth 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: eosinophil-mediated killing of helminths?

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.