Blood and immunity: affinity maturation: practice question

A Physiology 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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Physiology · Blood and immunity: affinity maturation

Sample item

During a prolonged immune response, antibodies produced against the same antigen bind with progressively higher affinity. Which process in the germinal centre is responsible?

AComplement-mediated opsonisation of the antigenBVDJ recombination at the pre-B cell stageCClass-switch recombination of the constant regionDSomatic hypermutation of variable regions, with selection of high-affinity B-cell clones

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

The answer and the reasoning

D. Somatic hypermutation of variable regions, with selection of high-affinity B-cell clones

In germinal centres, activation-induced cytidine deaminase introduces point mutations into the variable region genes. B cells whose receptors bind antigen better receive survival signals from follicular dendritic cells and T follicular helper cells, so average affinity rises. Class switching changes the isotype, not the affinity.

Option by option

A. Complement-mediated opsonisation of the antigen
Opsonisation enhances phagocytosis and does not change antibody affinity.
B. VDJ recombination at the pre-B cell stage
VDJ recombination generates the initial repertoire in bone marrow before antigen exposure.
C. Class-switch recombination of the constant region
Class switching changes the heavy chain constant region and the effector function, not the affinity.
D. Somatic hypermutation of variable regions, with selection of high-affinity B-cell clones (correct)
Correct. Mutation of variable regions followed by selection raises affinity.

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 Physiology question

What is the answer to this Physiology question?

The best answer is D, Somatic hypermutation of variable regions, with selection of high-affinity B-cell clones. In germinal centres, activation-induced cytidine deaminase introduces point mutations into the variable region genes.

Why is "Complement-mediated opsonisation of the antigen" not the answer?

Opsonisation enhances phagocytosis and does not change antibody affinity.

Why is "VDJ recombination at the pre-B cell stage" not the answer?

VDJ recombination generates the initial repertoire in bone marrow before antigen exposure.

Why is "Class-switch recombination of the constant region" not the answer?

Class switching changes the heavy chain constant region and the effector function, not the affinity.

What concept does this question test?

It tests Blood and immunity: affinity maturation in Physiology. B cells whose receptors bind antigen better receive survival signals from follicular dendritic cells and T follicular helper cells, so average affinity rises. Class switching changes the isotype, not the affinity.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Blood and immunity: affinity maturation?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.