Final answer:
Tissue originating from identical twins or with the same HLA is known as syngeneic tissue. Since identical twins share the same genetic makeup, they have identical HLAs, which is crucial for the success of tissue transplants such as bone marrow transplants.
Step-by-step explanation:
Tissue that originates from identical twins or individuals who have the same human leukocyte antigen (HLA) is known as syngeneic tissue. Syngeneic transplants are uncommon, typically occurring between identical twins, because they are the only individuals who share the same genetic makeup and, consequently, identical HLAs. The significance of HLA matching in tissue transplantation is due to MHC molecules, which can cause a recipient's immune system to reject a transplant if the HLAs are different. Therefore, a good HLA match is essential to minimize the risk of transplant rejection and complications such as graft-versus-host disease (GVHD). With identical twins sharing the same genetic material, they inherently provide a perfect HLA match for each other, significantly reducing the risk of rejection during tissue transplants.
When considering non-syngeneic transplants, it's important to test for HLA compatibility. For bone marrow transplants, donors and recipients are usually tested for up to ten HLA markers, and a close match is imperative for a successful transplant. Identical twins, with their identical HLA markers, naturally surpass this compatibility requirement, making them ideal donors for each other.