Britannica Sources used in this answer

Why are blood groups checked before an organ transplant?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Kidney transplant — transplant British surgeon Andrew Ready flushing a donated kidney during a transplant at Queen Elizabeth Hospital, Birmingham, England, 2006.

Blood groups are checked before an organ transplant because the ABO antigens are widely distributed throughout the tissues of the body. While these antigens are primarily associated with red blood cells, their presence in other tissues means that an ABO-incompatible organ can trigger an immune reaction, potentially leading to graft rejection.12

Surgeons generally prefer to use organs that are matched to the recipient’s blood group to minimize the risk of the recipient's immune system attacking the foreign tissue. Because the immune system is designed to distinguish between self and nonself substances, preexisting antibodies against donor antigens can cause rapid, irreversible rejection of the transplant.134

Although some successful transplants have occurred despite ABO incompatibility, matching remains a critical component of the immunologic profile used to select a suitable donor. In cases where a match is not possible, medical teams may employ desensitization therapy to filter out harmful antibodies from the patient's blood before the procedure.13