Transplantation of tissues/organs to save certain patients often fails due to rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?

Options

A. Auto - immune response
B. Humoral immune response
C. Physiological immune response
D. Cell - mediated immune response

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the type of immune response responsible for the rejection of transplanted tissues or organs in patients.

2. **Identifying the Rejection Mechanism**: Organ transplantation rejection occurs when the recipient's immune system recognizes the transplanted organ as foreign. This leads to an immune response against the transplanted tissue.

3. **Types of Immune Responses**: There are two main types of immune responses:
- **Humoral (Antibody-mediated) Immunity**: Involves B-cells and the production of antibodies.
- **Cell-mediated Immunity**: Involves T-cells and does not rely on antibodies.

4. **Role of T-cells in Rejection**: The rejection of transplanted organs is primarily mediated by T-cells, particularly:
- **T-helper cells**: Help activate other immune cells.
- **T-killer (cytotoxic) cells**: Directly kill the cells of the transplanted organ recognized as foreign.

5. **Conclusion**: The immune response responsible for the rejection of transplanted tissues or organs is the **cell-mediated immune response**.

6. **Final Answer**: The correct answer to the question is **cell-mediated immune response**.

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