Immunology: idiotype and allotype: 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: idiotype and allotype

Sample item

An anti-idiotype antibody is raised against a particular monoclonal antibody. Which part of the antibody does it recognise?

AAllelic variants in the heavy chain constant regionBThe hinge region disulphide bondsCUnique determinants in the antigen-binding variable regionDThe constant region shared by all antibodies of that class

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

The answer and the reasoning

C. Unique determinants in the antigen-binding variable region

Idiotypes are antigenic determinants formed by the unique variable region sequences, including the hypervariable loops, of a particular antibody. Isotypes are class and subclass differences in constant regions present in all individuals, and allotypes are allelic differences between individuals in constant regions.

Option by option

A. Allelic variants in the heavy chain constant region
Allelic differences in constant regions describe allotypes.
B. The hinge region disulphide bonds
Disulphide bonds are covalent links, not antigenic determinants that define the idiotype.
C. Unique determinants in the antigen-binding variable region (correct)
Correct. The idiotype lies in the variable region unique to each antibody.
D. The constant region shared by all antibodies of that class
Determinants of the constant region shared by the class describe the isotype.

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, Unique determinants in the antigen-binding variable region. Idiotypes are antigenic determinants formed by the unique variable region sequences, including the hypervariable loops, of a particular antibody.

Why is "Allelic variants in the heavy chain constant region" not the answer?

Allelic differences in constant regions describe allotypes.

Why is "The hinge region disulphide bonds" not the answer?

Disulphide bonds are covalent links, not antigenic determinants that define the idiotype.

Why is "The constant region shared by all antibodies of that class" not the answer?

Determinants of the constant region shared by the class describe the isotype.

What concept does this question test?

It tests Immunology: idiotype and allotype in Microbiology. Isotypes are class and subclass differences in constant regions present in all individuals, and allotypes are allelic differences between individuals in constant regions.

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: idiotype and allotype?

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.