Excessive and inappropriate immune response to an antigen is:

Options

A. anaphylaxis
B. multiple sclerosis
C. allergy
D. immune diffiency

Answer

To solve the question "Excessive and inappropriate immune response to an antigen is:", we will analyze the options provided and identify the correct answer based on our understanding of the immune response.

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for a term that describes an excessive and inappropriate immune response to an antigen. This suggests that we are looking for a condition where the immune system reacts too strongly or inappropriately to a substance that is typically harmless.

2. **Review the Options**:
- **Option 1: Anaphylaxis** - This is a severe allergic reaction that can occur rapidly. While it is an excessive immune response, it is a specific type of allergic reaction rather than a general term for inappropriate immune responses.
- **Option 2: Multiple Sclerosis** - This is an autoimmune disorder where the immune system attacks the nervous system. It does not fit the description of an excessive response to an antigen in the context of allergies.
- **Option 3: Allergy** - This term refers to an excessive and inappropriate immune response to typically harmless substances (allergens). This fits the definition provided in the question.
- **Option 4: Immune Deficiency** - This refers to a reduced ability of the immune system to fight infections and diseases, which is the opposite of an excessive response.

3. **Identify the Correct Answer**: Based on the analysis of the options, the term that best describes an excessive and inappropriate immune response to an antigen is **Option 3: Allergy**.

4. **Conclusion**: Therefore, the correct answer to the question is **Allergy**.