Which of the following is an incorrect statement about the second response of the body against a previously infected antigen?

Options

A. The main antibody formed during the secondary response againt a previously encountered antigen is IgM.
B. The secondary immune response of the body is based on memory cells
C. The immune response against a previously infected antigen is also known as anamnestic response
D. The secondary immune response given effective immunity

Answer

To solve the question regarding the incorrect statement about the second response of the body against a previously infected antigen, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Primary and Secondary Immune Responses**:
- The primary immune response occurs when the body is exposed to an antigen for the first time. This response is characterized by the production of antibodies, primarily IgM, and takes longer (about 4 to 7 days or even weeks) to develop.
- The secondary immune response occurs when the body is exposed to the same antigen again. This response is faster and more robust due to the presence of memory cells formed during the primary response.

2. **Identify the Main Antibodies Produced**:
- During the primary response, the main antibody produced is IgM.
- In the secondary response, the main antibody produced is IgG, although a small amount of IgM may also be produced.

3. **Evaluate the Statements**:
- The question asks to identify the incorrect statement regarding the secondary response.
- One statement claims that the main antibody formed during the secondary response is IgM. This is incorrect because IgM is primarily associated with the primary response.

4. **Confirm Other Statements**:
- Other statements may include:
- The secondary response is based on memory cells (correct).
- The immune response against previously infected antigens is known as the anamnestic response (correct).
- The secondary response is more rapid and effective compared to the primary response (correct).

5. **Conclusion**:
- The incorrect statement is that the main antibody formed during the secondary response is IgM. The correct antibody is IgG.

### Final Answer:
The incorrect statement is that the main antibody formed during the secondary response against a previously encountered antigen is IgM.

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