Hyperacute rejection occurs most commonly in which organ: March 2007

Ans. B: Kidney Hyperacute rejection is a complement-mediated response in recipients with pre-existing antibodies to the donor (for example, ABO blood type antibodies). Hyperacute rejection occurs within minutes and the transplant must be immediately removed to prevent a severe systemic inflammatory response. Rapid agglutination of the blood occurs. This is a paicular risk in kidney transplants, and so a prospective cytotoxic crossmatch is performed prior to kidney transplantation to ensure that antibodies to the donor are not present. Hyperacute rejection is analogous to a blood transfusion reaction as it is a humoral-mediated immune response. For other organs, hyperacute rejection is prevented by transplanting only ABO-compatible grafts. Hyperacute rejection is not significant in liver allografts and cellular transplants because these tissues have remarkable regenerative abilities. Hyperacute rejection is the outcome of xenotransplanted organ in non-immunosuppressed recipients