Xenotransplantation.

The need for an alternative source of donor organs, together with the expansion of scientific data in this field, has focused attention on xenotransplantion as a possible alternative to allotransplantation in the treatment of patients with end-stage disease of vital organs. However, xenotransplantation is rarely successful. Not only are the immunological barriers to the acceptance of xenogeneic tissue more powerful than those seen in allotransplantation, but the potential for the transmission of xenograft-associated zoonoses to the human host at the time of transplantation is also present. In addition, data on the physiological performance of the xenograft in the human environment are lacking, although a few functioning xenografts have been shown to be capable of supporting human life. Although progress has been made in clarifying some of the barriers to xenotransplantation and in defining appropriate therapeutic interventions, including interventions aimed at the removal of natural antibody and at the limitation of complement activation, xenotransplantation is not yet a viable alternative to allotransplantation in the clinical setting.