How many are example of passive immunity?
P. Vaccination
Q. crossing of antibodies from mother to foetus through the placenta
R. Graft rejection
S. Injections given to patents of snakebite
T. Tetanus antitoxin

Options

A. Two
B. Three
C. Four
D. Five

Answer

To determine how many examples of passive immunity are present in the given options, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Passive Immunity**:
- Passive immunity is defined as immunity acquired through the transfer of antibodies produced outside the body. This can occur naturally (e.g., from mother to fetus) or artificially (e.g., through injections).

2. **Analyzing Option P: Vaccination**:
- Vaccination involves the introduction of antigens to stimulate the body to produce its own antibodies. This is an example of **active immunity**, not passive immunity.
- **Conclusion**: Not an example of passive immunity.

3. **Analyzing Option Q: Crossing of antibodies from mother to fetus through the placenta**:
- This process involves the transfer of maternal antibodies to the fetus, providing the fetus with immunity without the fetus having to produce its own antibodies.
- **Conclusion**: This is an example of passive immunity.

4. **Analyzing Option R: Graft rejection**:
- Graft rejection is a response by the immune system to reject transplanted tissue. This involves cellular immunity and is an adaptive immune response.
- **Conclusion**: Not an example of passive immunity.

5. **Analyzing Option S: Injections given to patients of snakebite**:
- In the case of snakebite, patients are given antivenom, which contains pre-formed antibodies. This is an artificial form of passive immunity.
- **Conclusion**: This is an example of passive immunity.

6. **Analyzing Option T: Tetanus antitoxin**:
- Tetanus antitoxin is an injection that provides immediate immunity by supplying pre-formed antibodies against the tetanus toxin. This is also an example of artificial passive immunity.
- **Conclusion**: This is an example of passive immunity.

### Final Count of Passive Immunity Examples:
- From the analysis:
- **Option Q**: Yes (Passive immunity)
- **Option R**: No (Not passive immunity)
- **Option S**: Yes (Passive immunity)
- **Option T**: Yes (Passive immunity)

Thus, there are **three examples of passive immunity**: Q, S, and T.

### Answer:
**3 examples of passive immunity.**

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