THE PROSPECTS FOR RENAL XENOTRANSPLANTATION

Xenotransplantation of non-human organs into human recipients has long been proposed as a possible strategy to overcome the acute shortage o f donor organs. However, vascular organ transplants to humans from phy logenetically disparate species such as the pig are not currently poss ible due to a rapid rejection process termed hyperacute rejection. Thi s process is initiated by the binding of host pre-formed 'natural anti bodies' to the donor vascular endothelium, activation of the host comp lement system and activation or injury of the donor endothelial cells, leading to intravascular coagulation and loss of the graft due to isc haemic necrosis within minutes to hours of engraftment. Prevention of natural antibody binding and complement activation is viewed as paramo unt to preventing hyperacute rejection. Even if hyperacute rejection c an be prevented, further barriers to successful discordant xenografts such as delayed xenograft rejection and a donor-directed cell-mediated rejection process will still represent major obstacles. This review e xamines recent advances being made in the various areas of xenograft r esearch and the potential clinical application of pig-to-human xenogra fts that these strategies may bring.