To prevent graft (kidney transplant) rejection, the principle is to use chemicals, which inhibit the entire activity of the immune system. When this occurs graft rejection is delayed. It has been shown that immunosupppression may make the patients more preen to develop cancers. One way of overcoming the problems of radiation and immunosuppression is to suppress only the cells responsible for rejection, normally the killer T-cells. In this way, the rest of the patients immune system would continue to function normally. The most promising approach is to treat the patient with monoclonal antibodies that recognize and destroy the killer T-cells. A monoclonal antibody has been developed, which is a very effective at preventing rejection of transplanted kidneys.