GATE BT 2019 • Q20
MCQ • 1 Mark
Section 2: General Biotechnology
Cell structure and signaling
Subtopic: Fundamentals of Cell structure and signaling
Question Statement:
Which one of the following is NOT a part of the human nonspecific defense system?
Options:
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(A) Interferon
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(B) Mucous
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(C) Saliva
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(D) Antibody
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2019 Q.20)**
**1. Governing Concept**:
- **Topic**: Immunology & Innate vs. Adaptive Immunity
- The human immune system comprises two arms:
- **Non-specific (Innate) immune defenses**: Provide immediate, antigen-independent physical, chemical, and cellular barriers:
- Mechanical / anatomical barriers: **Mucus**, skin, cilia.
- Secretory fluids: **Saliva** (contains lysozyme, lactoferrin), tears, gastric acid.
- Cytokines: **Interferons** ($\text{IFN}-\alpha/\beta$) antiviral signaling.
- **Specific (Adaptive) immune defenses**: Antigen-specific, clonally diversified responses mediated by T-cells and **Antibodies** (immunoglobulins produced by differentiated plasma B-cells).
- Therefore, **Antibodies** are NOT part of the non-specific defense system; they represent the hallmark of adaptive humoral immunity.
**2. Option Analysis**:
- **Option (A) [Interferon] is INCORRECT**: Innate cytokine providing non-specific antiviral resistance.
- **Option (B) [Mucous] is INCORRECT**: Physical/chemical innate barrier trapping particulates.
- **Option (C) [Saliva] is INCORRECT**: Contains innate antimicrobial enzymes (lysozyme).
- **Option (D) [Antibody] is CORRECT**: Component of specific adaptive humoral immunity.
**3. Final Answer**:
- **Correct Choice**: **D**
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