Naturally active acquired immunity is given by:

Options

A. Vaccination
B. Antiserum
C. NK cells
D. Infections.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Active Immunity**: Active immunity is a type of immunity where the immune system actively produces antibodies in response to a pathogen. This can occur naturally when the body encounters a pathogen.

2. **Natural Acquisition of Active Immunity**: Naturally active acquired immunity occurs when a person is exposed to a pathogen (such as bacteria, viruses, or fungi) and the immune system recognizes it as foreign.

3. **Immune Response Activation**: Upon recognizing the pathogen, the immune system is activated, leading to the generation of an immune response. This includes the production of antibodies specific to that pathogen.

4. **Memory Formation**: The immune system also creates memory cells during this process. These memory cells allow the body to remember the pathogen, so if it is encountered again in the future, the immune system can respond more quickly and effectively.

5. **Conclusion**: Therefore, naturally active acquired immunity is given by infections, as they stimulate the immune system to produce antibodies and memory cells against the pathogen.

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