Organ transplants save the lives of thousands of people every year, and continuing research is making that process increasingly safe. The main problem with organ transplantation is the organ rejection that occurs if the recipient immune system is not compatible with the donor cells. This causes organ failure, and long-term immunosuppression is often required. While this immunosuppression keeps the allograft healthy, it has serious side effects on both the organ and immune systems of the recipient. Further research into immunosuppression can lead to safer transplants methods and post-surgical therapies. The ultimate goal of this research is to create an environment of complete tolerance, allowing the immunosuppression to be stopped with no ill effects.