A kidney transplant from one identical twin to another is an example of what type of graft?

• A. Allograft
• B. Autograft
• C. Isograft
• D. Xenograft

Answer: (C)

The main idea is grafts between genetically identical individuals. A kidney transplant from one identical twin to another is a syngeneic or isograft, because the donor and recipient share the same genetic makeup, including nearly identical HLA antigens. That makes the immune system see the transplanted tissue as essentially self, greatly reducing the risk of rejection and often diminishing or eliminating the need for immunosuppressive therapy.

In contrast, a graft from a different person (allograft) carries genetic differences that can trigger rejection, and a graft from a different species (xenograft) would provoke a strong immune response. An autograft would be tissue moved within the same person, which also avoids rejection but isn’t the scenario described here.