Future directions in transplantation.

Transplantation has become an established treatment for many diseases where organ replacement is the best or perhaps the only option, but it has not reached its full potential. The use of fetal and infant donors raises ethical problems, as does the use of other species for xenografts. Legal problems include the drafting of appropriate legislation to maximise the donor pool. Economic limitations are imposed by the competition for funding with other areas of medicine. Transplantation of cells, tissues, and organs is rapidly being expanded. Exciting progress in experimental models of new methods of immunosuppression may lead to immunological tolerance of grafts so that chronic non-specific immunosuppression becomes a thing of the past. Xenografts will probably have to become a major source of organs as transplantation is extended to more patients and a broader range of diseases. Genetic engineering may alleviate the problem of supply in some instances; free cell transplants of genetically modified cells are being studied.