The future of organ transplantation: from the laboratory to the clinic

This is a short review of tolerance from the point of view of the clinician . Various examples of tolerance occurring in patients and animal models tha t relate to the clinical experience are described. It is suggested that the re may be different mechanisms by which tolerance is achieved, but from the patient's point of view operational tolerance is the goal, whereby, after a short induction procedure, the patient will maintain good function in the grafted organ indefinitely without maintenance immunosuppression. It is po inted out that such a goal may be difficult to achieve with any given proto col due to the enormous variation between donors and recipients of organ gr afts of tissue matching, innate immune reactivity and susceptibility to dis turbance of a tolerant state by infections or allergic reactions. Thus the case is made for prope or almost tolerance in which graft acceptance is mai ntained by a low, non-toxic dosage of maintenance immunosuppression that ma y not be required indefinitely.