Classification of Rejection in Host Recipients in Xenotransplantation

Glycome difference between human and non-human species is the most basic concept as a main barrier of xenotransplantation. Determination of xenogeneic carbohydrate antigens different from interspecies and different species is the first and the crucial step because cell surfaced carbohydrates are biosynthesized by diverse and various glycosyltransferases. They are bound by preformed natural Abs or de novo biosynthesized Abs. They are subjects of the reaction to incompatible blood products, tissues, and organs. In the vascular endothelium, the transplanted endothelial cells of the donor organ are the first lines and contacting sites with the host recipient’s blood in organ transplantation. In vascular endothelium, endothelial cells regularly express their self-protecting substances in terms of anti-inflammatory molecule and anticoagulative agents on cell surfaces, which are naturally crucial for the blood anticoagulation and for homeostatic self-protection. Genetically distinct differences are well known between the donors and host recipients, which are the basic causing factors for the rejection during cell, tissue, and organ xenotransplantation in the recipient immune system, consequently resulting in complete failure of the transplantation. Several biological incompatibilities between pigs and humans are the fundamental basis to prevent clinical xenotransplantation. Indeed, pig xenogeneic organs are immunologically rejected by the immune system of human by the most basic AMR. Xenoantigenic grafts are the major subject of immune rejections in mode of species- and tissue-specific carbohydrate antigens.