Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
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
Options:
(A) P-3, Q-1, R-4, S-2
(B) P-4, Q-3, R-1, S-2
(C) P-3, Q-4, R-2, S-1
(D) P-3, Q-2, R-4, S-1
Official Answer Key:
A
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.36)**
**1. Governing Concept**:
- **Topic**: Immunology & Immune Tolerance Mechanisms
- Matching tolerance mechanisms with biological outcomes:
- **P. Anergy** $\rightarrow$ Functional unresponsiveness of lymphocytes when antigen is presented by APCs **lacking co-stimulatory molecules** (CD80/CD86 binding CD28) $\rightarrow$ **3**
- **Q. Activation-induced cell death (AICD)** $\rightarrow$ **Elimination of activated effector T-cells** via Fas/FasL apoptosis after successful clearance of antigen $\rightarrow$ **1**
- **R. Receptor editing** $\rightarrow$ RAG re-expression during B-cell development in bone marrow leading to light-chain rearrangement to **eliminate/rescue autoreactive B-cells** $\rightarrow$ **4**
- **S. Regulatory T-cells (Tregs)** $\rightarrow$ CD4+CD25+FoxP3+ T-cells that mediate **peripheral tolerance by inhibiting auto-reactive T-cells** via IL-10, TGF-$\beta$, CTLA-4 $\rightarrow$ **2**
**2. Option Analysis**:
- **Option (A) [P-3, Q-1, R-4, S-2] is CORRECT**: Every immune tolerance mechanism is perfectly matched to its definitive cellular outcome.
- **Option (B) is INCORRECT**: Misassigns anergy to B-cell elimination.
- **Option (C) is INCORRECT**: Misassigns AICD to B-cell elimination.
- **Option (D) is INCORRECT**: Inverts AICD and Treg outcomes.
**3. Final Answer**:
- **Correct Choice**: **A**
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