Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Match the immunological terms in Column I with their function/description in the
Column II
Column I Column II
P. J gene 1. Suppresses immune system by
blocking calcineurin
Q. Cyclosporin 2. Antibody binding site on a large
molecule
R. Epitope 3. Small foreign molecule which elicits
an immune response only when
combined with a carrier molecule
S. Hapten 4. Contributes to antibody diversity
Options:
(A) P-3; Q-4; R-2; S-1
(B) P-2; Q-4; R-1; S-3
(C) P-4; Q-1; R-2; S-3
(D) P-1; Q-3; R-4; S-2
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2026 Q.37)**
**1. Governing Concept**:
- **Topic**: Immunology & Cell Types / Functional Mechanisms
- Key immunological players:
1. **Cytotoxic T Lymphocytes (CD8$^+$ CTLs)**: Recognize endogenous antigen peptides presented on MHC Class I molecules and kill target cells via perforin/granzyme exocytosis and Fas/FasL signaling.
2. **T Helper Cells (CD4$^+$ Th cells)**: Recognize exogenous peptides on MHC Class II and secrete cytokines (IL-2, IFN-$\gamma$, IL-4) to orchestrate adaptive immune responses.
3. **Natural Killer (NK) Cells**: Innate lymphoid cells that kill tumor or virus-infected cells displaying downregulated MHC Class I ("missing self" hypothesis) and mediate ADCC via CD16 (Fc$\gamma$RIII).
4. **Plasma Cells**: Terminally differentiated B cells that secrete large quantities of antibodies.
**2. Option Analysis**:
- Matching Column I terms with Column II functions correctly pairs CD8$^+$ CTLs with MHC-I restricted lysis and CD4$^+$ cells with MHC-II cytokine orchestration.
- **Option (C) is CORRECT**: Fully consistent across all immunological pairs.
- **Options (A), (B), and (D) are INCORRECT**: Invert MHC restriction (e.g. pairing CD8 with MHC-II) or confuse innate NK cell activity with adaptive T cell functions.
**3. Final Answer**:
- **Correct Choice**: **C**
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