CD47 in xenograft rejection and tolerance induction

Robust immune responses to xenografts remain a major obstacle to clinical translation of xenotransplantation, which could otherwise be a potential solution to the worldwide shortage of organ donors. The more vigorous xenograft rejection relative to allograft rejection is largely accounted for by the extensive genetic disparities between the donor and recipient. Xenografts activate host immunity not only by expressing immunogenic xenoantigens that provide the targets for immune recognition and rejection, but also by lacking ligands for the host immune inhibitory receptors. This review is focused on recent findings regarding the role of CD47, a ligand of an immune inhibitory receptor SIRP alpha, in xenograft rejection and induction of xenotolerance.