Final answer:
Doctors seek a kidney transplant donor with MHC (HLA) genes that match the recipient to minimize the risk of organ rejection. Even with good genetic matching, immunosuppressive therapy is often necessary, and patients typically require lifelong immunosuppressants.
Step-by-step explanation:
When doctors are looking for a suitable donor for a kidney transplant, they are primarily looking for someone whose tissues have self markers, known as MHC (HLA) genes, that are similar to those of the recipient. The similarity in these genes between the donor's and recipient's tissues is crucial because it reduces the likelihood of organ rejection after the transplant. However, even with a good genetic match, transplant recipients often require immunosuppressive therapy to further minimize the risk of rejection.
It is important to note that while matching MHC genes lower the risk of rejection, other gene products can also stimulate immune responses against grafted tissue, which means that no transplant is likely to be completely free of rejection risks. Consequently, recipients typically need to remain on immunosuppressant drugs for life, which can make them more susceptible to infections and transplant-related malignancies.
The correct answer to the student's question is (a) because the presence of similar MHC gene products between the donor and recipient plays a vital role in preventing tissue rejection. The other immune system's components, such as natural killer cells, macrophages, and T cells, are also essential in the body's response to transplanted organs but are not the primary focus when selecting a donor.