Immunology: innate immunity: 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: innate immunity

Sample item

In Gram-negative sepsis, macrophages release large amounts of TNF-alpha and IL-1 after recognising bacterial lipopolysaccharide. Which receptor complex is chiefly responsible for this recognition?

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

The answer and the reasoning

C. Toll-like receptor 4 with MD-2 and CD14

Toll-like receptor 4, together with the co-receptors MD-2 and CD14, binds lipopolysaccharide and triggers NF-kappa B signalling and proinflammatory cytokine release. TLR5 recognises flagellin, TLR3 detects double-stranded viral RNA, and TLR9 detects unmethylated CpG DNA in endosomes.

Option by option

  • A. Toll-like receptor 5

    TLR5 recognises bacterial flagellin, not lipopolysaccharide.

  • B. Toll-like receptor 3

    TLR3 senses viral double-stranded RNA in endosomes.

  • C. Toll-like receptor 4 with MD-2 and CD14 (correct)

    Correct. TLR4 is the pattern recognition receptor for endotoxin.

  • D. Toll-like receptor 9

    TLR9 senses unmethylated CpG motifs of bacterial and viral DNA.

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, Toll-like receptor 4 with MD-2 and CD14. Toll-like receptor 4, together with the co-receptors MD-2 and CD14, binds lipopolysaccharide and triggers NF-kappa B signalling and proinflammatory cytokine release.

Why is "Toll-like receptor 5" not the answer?

TLR5 recognises bacterial flagellin, not lipopolysaccharide.

Why is "Toll-like receptor 3" not the answer?

TLR3 senses viral double-stranded RNA in endosomes.

Why is "Toll-like receptor 9" not the answer?

TLR9 senses unmethylated CpG motifs of bacterial and viral DNA.

What concept does this question test?

It tests Immunology: innate immunity in Microbiology. TLR5 recognises flagellin, TLR3 detects double-stranded viral RNA, and TLR9 detects unmethylated CpG DNA in endosomes.

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: innate immunity?

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.