Conversion of antigen into harmless insoluble matter by binding of antibody to it is

Options

A. Complement system
B. Opsonization
C. Activation
D. Agglutination

Answer

To solve the question regarding the conversion of antigen into harmless insoluble matter by binding of antibody to it, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Antigens and Antibodies**:
- Antigens are foreign substances that enter the body and trigger an immune response. Antibodies are proteins produced by the immune system to identify and neutralize these antigens.

2. **Mechanism of Action**:
- When an antigen enters the body, the immune system recognizes it as a threat and produces antibodies specific to that antigen.

3. **Binding Process**:
- The antibodies bind to the antigens. This binding is crucial as it marks the antigens for destruction and helps in neutralizing their harmful effects.

4. **Formation of Insoluble Matter**:
- The binding of antibodies to antigens can lead to the formation of a complex that is insoluble. This process effectively clumps the antigens together, making them easier for immune cells to target and eliminate.

5. **Identifying the Correct Term**:
- The process of converting antigens into harmless insoluble matter through the binding of antibodies is specifically referred to as "agglutination."

6. **Conclusion**:
- Therefore, the correct answer to the question is **agglutination**.

### Final Answer:
**Agglutination**