Final answer:
Graft rejection is typically caused by the immune system recognizing transplanted tissue as foreign. Autografts are unlikely to be rejected, while allografts, such as hepatic transplants, can cause rejection. Transplants from identical twins usually do not result in rejection, nor does the use of immunosuppressive drugs, which aim to prevent it.
Step-by-step explanation:
Graft rejection may be caused by factors related to the genetic differences between the donor's and the recipient's tissues. Not all transplantations have the same risk of rejection. An autograft, which involves tissue transplanted from one area of the body to another in the same individual, such as skin grafts on a burn patient, is unlikely to be rejected. In contrast, a hepatic allograft involves transplanting liver tissue from one genetically distinct individual to another within the same species, and it can cause rejection unless the donor and recipient are genetically compatible.
Transplantation of a kidney from an identical twin is an example of an isograft and typically does not result in rejection due to the genetic identity of the twin donors. Moreover, the use of high doses of immunosuppressive drugs is intended to prevent rejection; it is not a cause of rejection. Instead, inappropriate or insufficient immunosuppressive therapy might lead to rejection by failing to adequately suppress the immune response against the graft.
Graft-versus-host disease (GVHD), on the other hand, occurs primarily in bone marrow transplants, where the transplanted tissue attacks the recipient's body cells. However, this specific issue relates to bone marrow transplants, not kidney or liver transplants, which were mentioned in the previous scenarios.