Final answer:
Madison's kidney donation to her sister is an allograft, which is an organ transplant from one person to another within the same species. Blood relatives are preferred donors due to similar HLAs, reducing rejection risks. Immunosuppression via drugs is key post-transplant to avoid organ rejection.
Step-by-step explanation:
Madison wants to give a kidney to her older sister, which is an example of an allograft. This type of organ transplant involves transferring an organ from one person to another within the same species, but who are not genetically identical. This differs from an autograft, where tissue is moved from one part of the body to another part on the same individual; an isograft, which would be a transplant between genetically identical twins; and a xenograft, where tissues are transplanted from a member of one species to a member of another species. Immunosuppressive drugs are typically used post-transplant to minimize the risk of organ rejection due to the recipient's immune system recognizing the donor organ as foreign.
Blood relatives are often preferred as organ donors because they are more likely to share similar genetic markers, such as human leukocyte antigens (HLAs), which decrease the chances of the recipient's immune system attacking the transplanted organ. Immunosuppression is critical after transplantation to prevent the immune system from responding to the transplanted organ as it would to a foreign pathogen, potentially leading to organ rejection. It involves the administration of immunosuppressive medication to reduce the activity of the patient's immune system, thus protecting the transplanted organ.