transplant

transplant

 or graft

Partial or complete organ or other body part removed from one site and attached at another. It may come from the same or a different person or an animal. One from the same person—most often a skin graft—is not rejected. Transplants from another person or, especially, an animal are rejected unless they are unusually compatible or have no blood vessels (e.g., the cornea), or if the recipient's immune reaction is suppressed by lifelong drug treatment. Transplanted tissues must match (by blood tests) more closely than blood transfusions. Monoclonal antibodies targeting the cells that cause rejection hold great promise. Tests are now under way with monoclonal antibodies that react with antigens present only on T cells that are participating in rejection, sparing the rest. Rejection matters less in skin grafts, which may need to last only weeks, and bone grafts, whose structure remains after the cells die. In bone-marrow transplants, the donor's marrow cells may attack the recipient's tissues, often fatally. Lung transplants have greater chance of success as part of a heart-and-lung transplant. See also heart transplant, kidney transplant.