Since the development of transplantation of tissues, much effort has been directed towards the acceptance of transplanted grafts. Many methods have been developed to prevent or delay the rejection reaction. Some of them are used in clinical transplantation, involving immunosuppression of the host by certain drugs, hormones and by anti lymphocyte serum, which contains antibodies directed against the lymphocytes of the host. These methods, if carefully applied, may indeed prevent rejection of the grafts in a proportion of the patients. However, treatment with these drugs can be deleterious for the host, for suppression of the immune response increases the susceptibility for infection and probably also for tumors. In fact, many recipients of organ transplants still die from sepsis. Thus, any type of immunosuppression is still associated with a noxious effect on the host. A solution for these transplantation problems might be provided by the oldest principle in the achievement of graft acceptance, namely enhancement. Recently Snell defined enhancement as: the enhanced or prolonged growths of allografts, due to the presence in the graft recipient of allo-antibody directed against the allo-antigens of the donor. In other words, a graft is protected by enhancing antibodies, that are not directed against the recipient as is the case for A.L.S., but against the donor antigens.

H. Muller
Erasmus University Rotterdam
Erasmus MC: University Medical Center Rotterdam