Which of the following organ is not involved in elicitation of immune response?

Options

A. Thymus
B. Spleen
C. Lymph nodes
D. Brain

Answer

**Step-by-Step Solution:**

1. **Understanding the Immune System**: The immune system is composed of various organs and cells that work together to defend the body against pathogens. Key components include the thymus, spleen, lymph nodes, bone marrow, and white blood cells (WBCs).

2. **Identifying Key Organs**: The primary organs involved in the elicitation of the immune response are:
- **Thymus**: Site of T-cell maturation.
- **Spleen**: Filters blood and helps in the immune response.
- **Lymph Nodes**: Act as filters for lymph fluid and house immune cells.
- **Bone Marrow**: Produces blood cells, including immune cells.

3. **Evaluating the Options**: The question asks for an organ that is not involved in the immune response. Among the organs listed, the brain is mentioned.

4. **Role of the Brain**: While the brain regulates and controls various bodily functions, it does not directly participate in the elicitation of the immune response. Its role is more about overall regulation rather than direct involvement in immune functions.

5. **Conclusion**: Therefore, the organ that is not involved in the elicitation of the immune response is the **brain**.

**Final Answer**: The brain is not involved in the elicitation of the immune response.

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