Immunological reaction against transplanted organ is mediated by-
**Core Concept**
The immunological reaction against a transplanted organ is primarily mediated by the immune system's response to foreign antigens. This involves **cell-mediated immunity** and **humoral immunity**, with various components of the immune system playing crucial roles. The reaction is driven by the recognition of **major histocompatibility complex (MHC)** molecules on the surface of the transplanted cells.
**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the general mechanism. The immune response to a transplanted organ involves **T cells** recognizing **MHC** molecules on the transplanted cells as foreign, leading to **T cell activation** and the initiation of an immune response. **B cells** also play a role by producing **antibodies** against the transplanted organ. This complex interplay of immune cells and molecules is critical in the rejection of transplanted organs.
**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific details of option A, we cannot provide a direct explanation for its incorrectness.
**Option B:** Similarly, without specifics, we cannot address why option B is incorrect.
**Option C:** And option C's incorrectness cannot be discussed without knowing its content.
**Option D:** The same applies to option D, as the details are necessary to explain its incorrectness.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **immunosuppressive drugs** are used to reduce the immune system's response to transplanted organs, thereby preventing rejection. Understanding the mechanisms of these drugs and the immune response is crucial for managing transplant patients.
**Correct Answer:** Correct Answer: D. Cell mediated immunity.