Isograft

An isograft is a transplant of tissue between genetically identical individuals, typically between monozygotic twins. It is also called a syngeneic graft. Because donor and recipient share nearly identical genetic makeup, the risk of immune rejection is markedly reduced with grafts from identical genetics compared with allografts from nonidentical donors.

In humans, the classic isograft occurs between identical twins. In animal research, isografts can be performed between inbred strains. Many isografts require little or no immunosuppression, though minor histocompatibility antigens can occasionally provoke a limited rejection response, and patients are still monitored for graft function.

Applications include solid organ or tissue grafting when an identical twin is available, as well as bone marrow or hematopoietic stem cell transplants. Isografts may reduce or eliminate graft-versus-host disease risk in hematopoietic transplants compared with unrelated donor grafts.

Limitations include scarcity of truly identical donors in humans, restricting clinical use largely to twin pairs or controlled animal studies. Nonimmune factors such as ischemia, infection, or tissue-specific rejection can still affect outcome. Ethical and biosafety considerations apply to research use.

See also: autograft, allograft, xenograft, syngeneic graft.