Xenotransplantation: problems and prospects.

Research in xenotransplantation has increased enormously in the last eight years. As the shortage of allogeneic organs has intensified, the possibility of using organs from pigs has become more attractive. Current data suggest that hyperacute rejection can be overcome in a clinically acceptable manner. However, additional likely rejection factors, probably related to endothelial cell activation, are being identified that likely lead to delayed xenograft rejection, a phenomenon that can occur in the absence of T lymphocytes. Reviewed here are various genetic engineering approaches that might help overcome these rejection factors, resulting eventually in a multi-transgene donor pig. Other concerns and current controversies in the field are also discussed.