Transplantation of tissues/organs fails often due to non-acceptance by the patient's body. Which type of cells is mainly responsible for such rejections ?

Options

A. `T_(H)-` cells
B. `T_(K)-` cell
C. B- cells
D. Plasma cells

Answer

To answer the question regarding which type of cells is mainly responsible for the rejection of transplanted tissues or organs, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Transplantation**: When an organ or tissue is transplanted from a donor to a recipient, the recipient's immune system may recognize the transplanted tissue as foreign.

2. **Immune Response**: The immune system has a mechanism to identify and attack foreign substances. This is crucial for the body's defense against pathogens but can lead to rejection in the case of transplants.

3. **Role of Lymphocytes**: The immune response involves various types of white blood cells, particularly lymphocytes. There are two main types of lymphocytes involved in the immune response: B lymphocytes and T lymphocytes.

4. **Cell-Mediated Immune Response**: The rejection of transplanted tissues is primarily mediated by T lymphocytes (also known as T cells). These cells are responsible for recognizing and attacking cells that are perceived as foreign.

5. **B Lymphocytes**: While B lymphocytes are involved in producing antibodies against foreign antigens, the immediate rejection response in organ transplantation is primarily due to T cells.

6. **Conclusion**: Therefore, the type of cells mainly responsible for the rejection of transplanted tissues or organs are T lymphocytes.

### Final Answer:
T lymphocytes (T cells) are mainly responsible for the rejection of transplanted tissues or organs.

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