D.P.T. vaccine in an example of

Options

A. passive immunity
B. active immunity
C. both A and B
D. interferon

Answer

### Step-by-Step Solution:

1. **Understanding the DPT Vaccine**:
- The DPT vaccine is a combination vaccine that protects against three infectious diseases: diphtheria, pertussis (whooping cough), and tetanus.

2. **Components of the DPT Vaccine**:
- The vaccine contains diphtheria and tetanus toxoids (inactivated toxins) and heat-killed cells of the bacteria that cause pertussis.

3. **Mechanism of Action**:
- When the DPT vaccine is administered, it introduces antigens into the body. The immune system responds by producing antibodies against these antigens.

4. **Classification of Immunity**:
- **Active Immunity**: This occurs when the body produces its own antibodies in response to an antigen. The DPT vaccine stimulates the immune system to create these antibodies.
- **Passive Immunity**: This involves the introduction of antibodies from an external source, rather than the body producing them itself.

5. **Conclusion**:
- Since the DPT vaccine leads to the production of antibodies by the immune system in response to the introduced antigens, it is classified as an example of **active immunity**.

### Final Answer:
The DPT vaccine is an example of **active immunity**.

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