Từ điển khoa học động vật vần XYZ | Xenotransplantation Biological Barrier Jeffrey L. Platt Mayo Clinic Rochester Minnesota . INTRODUCTION Xenotransplantation the transplantation of cells tissues or organs between individuals of different species is a subject of interest because it might be used to address a shortage of human organs for transplantation and for other purposes. While the potential applications of xenotransplantation are widely appreciated the biological hurdles have prevented all but a small number of experimental trials. BIOLOGICAL HURDLES TO XENOTRANSPLANTATION The biological hurdles to xenotransplantation are summarized subsequently and in recent reviews. 1 2 With certain notable exceptions the hurdles are a direct function of the phylogenetic distance between the graft and the recipient. Because of this consideration some have advocated using closely related species for example primates in the case of human recipients as a source of xenografts. However nonhuman primates are not sufficiently plentiful to provide organs needed to treat human disease and may harbor viruses potentially lethal to humans. Use of nonhuman primates also raises social and ethical controversy. For these reasons many in the field of transplantation have turned to the pig as a potential source of xenografts. Swine are plentiful and some strains such as the mini-pig have organs of appropriate size for use in humans. Further the pig can be genetically engineered. This article will therefore focus on the pig although what is mentioned for the pig would also apply to other nonprimate mammals. IMMUNOLOGICAL HURDLES TO XENOTRANSPLANTATION Many components of the immune system may target a xenograft Table 1 . The most important component may be xenoreactive natural antibodies. Xenoreactive natural antibodies are made by all immunocompetent humans and recognize predominantly Gala1-3Gal a saccharide synthesized by lower mammals and New World monkeys which have a functional a1 3galactosyltrans-ferase. Humans and Old
