Final answer:
Immunosuppressant is the term for medications that prevent donor tissue rejection in organ transplantation, and they work by suppressing the immune system. Blood relatives are preferred as donors due to greater genetic similarity, reducing the likelihood of organ rejection.
Step-by-step explanation:
The term that describes medication used to prevent the rejection of donor tissue is . These drugs, such as cyclosporine, are crucial in organ transplantation as they suppress the immune system's response to what it perceives as foreign tissue. This is necessary because the immune system can recognize proteins on the donor organ as foreign, leading to rejection of the transplanted organ. work, for example, by inhibiting the production of interleukin, a cytokine messenger that activates T cells which would otherwise attack the transplanted tissue.
One reason why are often preferred as organ donors is because of their similar genetic background, particularly in terms of their MHC (HLA) genes. The greater the similarity in these genes, the lesser the chance of organ rejection. The more polymorphisms there are between the donor's and the recipient's MHC molecules, the higher the likelihood of rejection, thus necessitating a rigorous regime of immunosuppression.