Body cells infected by viruses are destroyed mostly by

Options

A. IgA
B. Phagocytes
C. Natural antibodies
D. Natural killer cells

Answer

To solve the question "Body cells infected by viruses are destroyed mostly by," we will analyze each option provided and determine which one is primarily responsible for destroying virus-infected cells.

### Step-by-Step Solution:

1. **Understanding the Options**:
- We have four options to consider:
- Immunoglobulin A
- Phagocytes
- Natural antibodies
- Natural killer cells

2. **Analyzing Immunoglobulin A**:
- Immunoglobulin A (IgA) is primarily a secretory antibody found in mucosal areas (like saliva, tears, and breast milk).
- Its main function is to protect against bacterial infections rather than viral infections.
- **Conclusion**: IgA is not primarily responsible for destroying virus-infected cells.

3. **Analyzing Phagocytes**:
- Phagocytes, including macrophages and neutrophils, are part of the innate immune response.
- They are effective in engulfing and destroying bacteria and other foreign pathogens.
- However, they are not specifically effective against virus-infected cells.
- **Conclusion**: Phagocytes do not primarily destroy virus-infected cells.

4. **Analyzing Natural Antibodies**:
- Natural antibodies are produced by plasma cells and target various pathogens.
- They mainly act against bacteria and other antigens but are not specifically effective against viruses.
- **Conclusion**: Natural antibodies do not primarily destroy virus-infected cells.

5. **Analyzing Natural Killer Cells**:
- Natural killer (NK) cells are a type of cytotoxic lymphocyte that play a crucial role in the immune response against viral infections.
- They can recognize and destroy cells that are infected with viruses, making them highly effective in this role.
- **Conclusion**: Natural killer cells are primarily responsible for destroying virus-infected cells.

6. **Final Answer**:
- Based on the analysis, the correct answer is **Natural killer cells**.