All are true for transplanted kidney except
**Core Concept**
The human leukocyte antigen (HLA) system plays a crucial role in organ transplantation, particularly in kidney transplants. The HLA system is a group of genes that code for proteins responsible for the immune system's ability to distinguish between the body's own proteins and those of foreign invaders. In the context of transplantation, HLA matching is critical to reduce the risk of graft rejection.
**Why the Correct Answer is Right**
The correct answer, **D. HLA identity similarity seen in 1:100 people**, is incorrect because the actual likelihood of HLA identity between two unrelated individuals is extremely low, not 1:100. The chances of two individuals having identical HLA profiles are approximately 1 in 20,000 to 1 in 100,000, making it highly unlikely to encounter a perfect HLA match in the general population.
**Why Each Wrong Option is Incorrect**
**Option A:** Humoral antibody is responsible for rejection, which is true. Antibodies can be involved in the rejection process, particularly in hyperacute rejection, but this option is not the correct answer because it is not the only or the most relevant aspect of kidney transplant rejection.
**Option B:** CMI (cell-mediated immunity) is responsible for rejection, which is also true. CMI plays a crucial role in the rejection process, particularly in acute and chronic rejection. However, this option is not the correct answer because it is not the specific characteristic that distinguishes the correct answer from the others.
**Option C:** Previous blood transfusion can increase the risk of rejection, which is true. Previous blood transfusions can lead to sensitization against certain HLA antigens, increasing the risk of rejection in kidney transplant recipients.
**Clinical Pearl / High-Yield Fact**
A key aspect of kidney transplantation is HLA matching, which is critical to reduce the risk of graft rejection. A good HLA match can significantly improve graft survival and reduce the risk of rejection.
**✓ Correct Answer: D. HLA identity similarity seen in 1:100 people**