Which of the following is not true for interferon?

Options

A. These act outside the cells.
B. These are quick acting.
C. Their action is long lasting.
D. These act against viruses.

Answer

### Step-by-Step Solution:

1. **Understanding Interferons**: Interferons are proteins produced by cells in response to viral infections. They play a crucial role in the body's immune response, particularly in innate immunity.

2. **Analyzing the Options**:
- **Option 1**: "These act outside the cells."
- This statement is true. Interferons signal neighboring cells to produce antiviral proteins, acting outside the cells.
- **Option 2**: "These are quick acting."
- This statement is also true. Interferons can activate within 1 to 2 hours after a pathogen enters the body.
- **Option 3**: "Their action is long lasting."
- This statement is false. Interferons typically have a short duration of action, lasting about 24 to 48 hours before being inactivated.
- **Option 4**: "These act against the viruses."
- This statement is true. Interferons are primarily known for their antiviral properties.

3. **Identifying the Incorrect Statement**:
- After evaluating all the options, the only statement that is not true for interferons is Option 3, which claims that their action is long lasting.

4. **Conclusion**: The correct answer to the question "Which of the following is not true for interferon?" is Option 3.