AP BIOLOGY

Detailed explanation-1: -It is caused by the presence of pre-existing antibodies in the recipient that recognize antigens in the donor organ. These antigens are located on the endothelial lining of blood vessels within the transplanted organ and, once antibodies bind, will lead to the rapid activation of the complement system.

Detailed explanation-2: -T cell activation is central to graft rejection. Tissue destruction occurs due to direct T cell-mediated lysis of graft cells, T cell activation of accessory cells, alloantibody production, and/or complement activation.

Detailed explanation-3: -This is because the person’s immune system detects that the antigens on the cells of the organ are different or not “matched.” Mismatched organs, or organs that are not matched closely enough, can trigger a blood transfusion reaction or transplant rejection.

Detailed explanation-4: -The immune system’s white blood cells make specific proteins called antibodies and special cells called T cells that destroy the foreign cells. A transplanted organ is made entirely of cells with foreign (“nonself”) antigens which means the body will attack the transplanted organ.

Detailed explanation-5: -Transplant rejection is caused by allorecognition of a donor’s antigens by a recipient’s immune system. Interestingly, the antigens responsible for most strong rejection reactions are actually MHC molecules themselves.