Which of the following is not a part of innate immunity?

Options

A. T-cell
B. Macrophage
C. HCl in stomach
D. Skin

Answer

To solve the question "Which of the following is not a part of innate immunity?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand Innate Immunity**: Innate immunity is the first line of defense in the immune system. It includes physical barriers, chemical barriers, and various immune cells that respond quickly to pathogens.

2. **Evaluate the Options**:
- **Option A: T-cell**: T-cells are a type of lymphocyte that plays a central role in adaptive immunity, not innate immunity. Therefore, this option is a candidate for the answer.
- **Option B: Macrophage**: Macrophages are part of the innate immune system. They are phagocytic cells that engulf and digest pathogens. This option is not the answer.
- **Option C: HCl in stomach**: Hydrochloric acid (HCl) in the stomach acts as a chemical barrier that helps destroy pathogens. It is part of innate immunity. This option is not the answer.
- **Option D: Skin**: The skin acts as a physical barrier to pathogens and is also part of the innate immune system. This option is not the answer.

3. **Identify the Correct Answer**: Since T-cells are part of adaptive immunity and not innate immunity, the correct answer to the question is **Option A: T-cell**.

### Final Answer:
The option that is not a part of innate immunity is **T-cell**.

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