Which leucocytes of the following resist infections and are also associated with allergic reactions?

Options

A. Eosinophils
B. Basophils
C. Monocytes
D. Lymphocytes

Answer

To solve the question "Which leucocytes resist infections and are also associated with allergic reactions?", we can follow these steps:

### Step 1: Understand the Types of Leucocytes
Leucocytes, or white blood cells (WBCs), are crucial components of the immune system. They help the body fight infections and respond to allergic reactions. The main types of leucocytes include:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils

### Step 2: Analyze Each Type of Leucocyte
1. **Eosinophils**:
- Comprise about 2-3% of WBCs.
- They are known to resist infections, particularly those caused by parasites.
- They are also associated with allergic reactions, such as asthma and hay fever.

2. **Basophils**:
- Comprise about 0.5-1% of WBCs.
- They are involved in inflammatory reactions and release histamine during allergic responses but are not primarily responsible for resisting infections.

3. **Monocytes**:
- These are phagocytic cells that help destroy foreign organisms but are not specifically associated with allergic reactions.

4. **Lymphocytes**:
- Responsible for the immune response but do not directly resist infections in the same way as eosinophils.

### Step 3: Identify the Correct Answer
Based on the analysis:
- Eosinophils are the type of leucocyte that both resist infections (especially parasitic infections) and are associated with allergic reactions.

### Conclusion
The correct answer to the question is **Eosinophils**.

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