The physiology of nerve transplantation.

As microsurgical techniques improve, attempts to restore function after severe nerve injury place greater demands upon the use of nerve grafts. Viable Schwann cells within these grafts are necessary to maximize nerve regeneration. Progress in decreasing nerve allograft antigenicity and the host response through immunosuppression may provide results comparable to nerve autografts. Although pretreatment methods aimed at reducing allograft antigenicity have yielded inconsistent and overall unsatisfactory results, cryopreservation can maintain Schwann cell viability and shows promise as a means of tissue banking. In addition, tissue typing for MHC I or II antigens and advances in immunosuppressive therapy have rendered encouraging results in experimental models. The use of transplanted nerve allografts remains experimental, yet efforts to understand the host rejection response, advances in immunotherapy, and the development of neurotrophic factors continue to reveal significant benefits over standard treatment methods.