Q.39 Match the entries in Group I with those in Group II

J chain, Serpin, β2-microglobulin, and Artemis are key immunology proteins matched to functions like Ig multimerization, complement inhibition, MHC components, and VDJ recombination. This matching question tests core concepts in antibody structure, innate immunity, antigen presentation, and adaptive immunity lymphocyte development. The correct matching is option (C).

Group I Functions

J chain (P) enables multimerization of secretory IgA and IgM by linking heavy chains in pentameric IgM or dimeric IgA, essential for mucosal immunity.​
Serpin (Q), specifically C1 esterase inhibitor (serpin family), inhibits C1 complement activation, preventing classical pathway overactivation in hereditary angioedema.
β2-microglobulin (R) forms the invariant light chain of MHC class I molecules, stabilizing α-chain for CD8 T cell peptide presentation on nucleated cells.​
Artemis (S), a nuclease in the non-homologous end joining pathway, processes hairpins during VDJ recombination in the RAG1/2 recombinase complex for BCR/TCR diversity.​

Group II Meanings

1. VDJ recombinase complex: RAG1/2 enzymes with Artemis for B/T cell receptor gene rearrangement.

2. Component of MHC class I: β2-microglobulin.

3. B cell co-receptor complex: CD19/CD21/CD81, enhances BCR signaling (not matched here).

4. C1 complement inhibitor: Serpin superfamily member blocking C1r/C1s.

5. Component of MHC class II: Invariant chain (Ii/CD74), not β2-microglobulin.

6. Multimerization of IgA and IgM: J chain.​

Option Analysis

Option (A) P-3, Q-4, R-5, S-1 fails: J chain not B cell co-receptor (3); β2-microglobulin not MHC II (5).​
Option (B) P-6, Q-5, R-2, S-3 wrong: Serpin not MHC II (5); Artemis not B cell co-receptor (3).
Option (C) P-6, Q-4, R-2, S-1 correct: Matches J chain to Ig multimerization (6), Serpin to C1 inhibitor (4), β2-microglobulin to MHC I (2), Artemis to VDJ complex (1).
Option (D) P-3, Q-4, R-1, S-6 incorrect: J chain not co-receptor (3); β2-microglobulin unrelated to VDJ (1).

Exam Relevance

This MCQ appears in NEET PG, AIIMS, and INI-SS immunology sections, linking humoral immunity (J chain, complement), antigen presentation (MHC), and V(D)J recombination. Understanding serpin’s role in complement regulation and Artemis deficiency (SCID radiosensitive type) aids clinical correlations like angioedema and severe combined immunodeficiency.