GATE 2023 BT – Question 36
Match the immune tolerance mechanisms in Group I with their respective outcomes in Group II.
| Group I | Group II |
|---|---|
| P. Anergy | 1. Elimination of activated T-cells after antigen clearance |
| Q. Activation-induced cell death | 2. Inhibition of auto-reactive T-cells at periphery |
| R. Receptor editing | 3. Unresponsiveness to antigens due to lack of co-stimulatory molecules |
| S. Regulatory T-cells | 4. Elimination of auto-reactive B-cells |
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Correct answer: (A) P-3, Q-1, R-4, S-2
Explanation
Match the tolerance mechanism with its outcome.
- **P. Anergy:** a T cell that receives the antigen signal without **co-stimulation** (CD28 engagement) becomes functionally unresponsive. P-3.
- **Q. Activation-induced cell death:** after an immune response, repeated stimulation leads to Fas-mediated apoptosis that removes the **activated T cells** once the antigen has been cleared. Q-1.
- **R. Receptor editing:** a self-reactive immature B cell in the bone marrow re-arranges its light-chain genes to change its specificity, or is eliminated, so autoreactive B cells are removed. R-4.
- **S. Regulatory T cells:** suppress auto-reactive T cells in the periphery. S-2.
Match: **P-3, Q-1, R-4, S-2** (option A).
Official GATE 2023 answer key: https://gate2026.iitg.ac.in/doc/download/Answer_keys2023/BT_ANS_GATE2023.pdf