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. Seealso heart transplant, kidney transplant.
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Replacement of a diseased or damaged kidney with one from a living relative or a legally dead donor. The former's tissue type is more likely to match, reducing the chance of rejection; but removal puts the donor at risk, and a kidney from a dead donor is more likely to be available. The new kidney is implanted and its blood vessels and ureter sewn in place. A near-normal life may be resumed within two months, but the drugs that prevent rejection leave the patient vulnerable to infection. Seealso transplant.
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Procedure to remove a diseased heart and replace it with a healthy one from a legally dead donor. The first was performed in 1967 by Christiaan Barnard. The diseased heart is removed (except for some atrial tissue to preserve nerve connections to the natural pacemaker). The new heart is put in place and connected to the recipient's blood vessels. Patients and donors are matched for tissue type, but the patient's immune system must still be suppressed to prevent rejection (see immunosuppression). A successful transplant can enable the recipient to have an active life for many years.
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