Which of the following is incorrectly matched ?

Options

A. Primary lymphoid organ : MALT
B. Antibody that crosses placenta : lgG
C. Vaccination : Active immunity
D. Reservoirs of monocytes : spleen

Answer

To solve the question "Which of the following is incorrectly matched?", we need to analyze each option provided and determine if the pairs are correctly matched or not.

### Step-by-Step Solution:

1. **Identify the Options**:
We need to look at the options given in the question. The options include pairs of terms related to immunology.

2. **Analyze Option 1**:
- **Primary Lymphoid Organ**: This is matched with **Mucosa Associated Lymphoid Tissue (MALT)**.
- **Evaluation**: MALT is actually a secondary lymphoid tissue, not a primary lymphoid organ. Primary lymphoid organs include the thymus and bone marrow. Therefore, this option is incorrectly matched.

3. **Analyze Option 2**:
- **Antibody that crosses placenta**: This is matched with **Immunoglobulin G (IgG)**.
- **Evaluation**: This is a correct match. IgG is indeed the only antibody that can cross the placenta, providing passive immunity to the fetus.

4. **Analyze Option 3**:
- **Vaccination**: This is matched with **Active Immunity**.
- **Evaluation**: This is also a correct match. Vaccination stimulates the immune system to produce an immune response, which is classified as active immunity.

5. **Analyze Option 4**:
- **Reservoir of Monocytes**: This is matched with **Spleen**.
- **Evaluation**: This is a correct match as well. The spleen acts as a reservoir for monocytes and plays a role in filtering blood and immune response.

6. **Conclusion**:
After analyzing all the options, we find that the only incorrectly matched pair is **Option 1** (Primary Lymphoid Organ with MALT).

### Final Answer:
**Option 1 is incorrectly matched.**

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