Differentiate between active immunity and passive immunity.

Explanation

### Step-by-Step Solution:

1. **Definition of Active Immunity**:
- Active immunity is a type of immunity that develops when an individual is exposed to an antigen (a foreign substance such as a virus or bacteria). The body responds by producing its own antibodies against the antigen.

2. **Mechanism of Active Immunity**:
- When a person comes into contact with an antigen, their immune system recognizes it as foreign and activates the immune response. This involves the production of specific antibodies by B cells.

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