have been proposed as a treatment for severe autoimmune diseases. donor-specific hla antibodies have been found to be associated with graft failure in renal, heart, lung, and liver transplantation. these donor-specific hla antibodies can exist pretransplant as consequence of sensitization to prior transplants or through pregnancies, but also occur de novo post-transplantation. there is a clear link between the risk of hla antibody sensitisation and the donor-recipient hla (molecular) mismatch. hla matching for sick siblings main article: savior sibling in some diseases requiring hematopoietic stem cell transplantation, preimplantation genetic diagnosis may be used to give rise to a sibling with matching hla, although there are ethical considerations.