Select the correct statement about diseases and immunisation

Options

A. If due to some reason B and T lymphocytes are damaged, then the body will not produce antibodies against a pathogen.
B. Injection of dead or inactivated pathogens causes passive immunity.
C. Certain protozoans have been used in mass production of hepatitis B vaccine.
D. Injection of snake antivenom against snake bite is an example of active immunisation.

Answer

To solve the question regarding the correct statement about diseases and immunization, we will evaluate each option provided.

### Step-by-Step Solution:

1. **Evaluate Option 1**:
- Statement: "If due to some reason B and T lymphocytes are damaged, then the body will not produce antibodies against a pathogen."
- Explanation: This statement is correct. B and T lymphocytes are crucial components of the immune system. B cells are responsible for producing antibodies, while T cells help coordinate the immune response. If either of these cell types is damaged, the body cannot effectively produce antibodies to combat pathogens.

2. **Evaluate Option 2**:
- Statement: "Injection of dead or inactivated pathogens causes passive immunity."
- Explanation: This statement is incorrect. The injection of dead or inactivated pathogens (like in vaccines) stimulates the body to produce its own antibodies, leading to active immunity, not passive immunity.

3. **Evaluate Option 3**:
- Statement: "Certain protozoans have been used in mass production of hepatitis B vaccine."
- Explanation: This statement is also incorrect. The hepatitis B vaccine is produced using recombinant DNA technology, not protozoans. The virus is inactivated using formaldehyde.

4. **Evaluate Option 4**:
- Statement: "Injection of snake antivenom against snake bite is an example of active immunization."
- Explanation: This statement is incorrect. Antivenom is an example of passive immunization. It involves the transfer of antibodies from another organism (usually a horse or sheep) that has been immunized against the venom.

5. **Conclusion**:
- After evaluating all options, the only correct statement is the first one: "If due to some reason B and T lymphocytes are damaged, then the body will not produce antibodies against a pathogen."

### Final Answer:
The correct statement about diseases and immunization is: **"If due to some reason B and T lymphocytes are damaged, then the body will not produce antibodies against a pathogen."**