Transplanting organs from a donor with a different type of MHC protein to a recipient is called what?

Transplanting organs from a donor with a different type of MHC (Major Histocompatibility Complex) protein to a recipient is referred to as an allograft. Allografts involve transplantation between individuals of the same species but who have different genetic backgrounds, leading to variations in their MHC proteins. This is relevant because MHC proteins play a crucial role in the immune system's ability to recognize self versus non-self. When an allograft is performed, the recipient's immune system may recognize the donor's MHC proteins as foreign, which can trigger an immune response against the transplanted organ.

In contrast, an isograft refers to a transplant between genetically identical individuals, such as identical twins, where MHC proteins match perfectly. An autograft involves transplanting an organ or tissue from one part of an individual's body to another part of the same individual, thus there is no MHC mismatch. A xenograft involves transplantation between different species, which presents even more significant challenges related to immune rejection due to major differences in MHC proteins. Therefore, the correct identification of allograft for transplants involving different MHC proteins accurately reflects the underlying immunological principles at play.