[Transplantation from animal to man].
Because of a severe shortage of donor organs, organ transplantation therapy can only be offered to a fraction of all patients needing it. This has sparked an increasing interest in xenotransplantation. Transgenic pigs could potentially provide tissue and organs to thousands of patients on waiting lists world-wide. Xenografts may be used as bridges or as permanent alternatives to organ allotransplants. Clinical trials of transplantation of pig cells and tissues to treat diabetes and neurodegenerative disorders are in progress. The most striking immunologic obstacle to xenotransplantation of solid organs, that of hyperacute rejection, is close to being overcome. Next steps in research are to refine immunosuppression, improve our knowledge of physiology and to allow for small and strictly regulated clinical studies. However, the risk for the recipients from infectious agents, particularly retroviruses, and potential dissemination of these in the human population cannot be ignored and must be thoroughly investigated. Ethical, safety, and monitoring guidelines are needed to control the development of xenotransplantation.