Skin-specific alloantigens in miniature swine

Background. The acceptance of skin allografts has historically been among t he most challenging problems in the field of transplantation, attributed, a t least in part, to the existence of antigens expressed by skin but not by other tissues. Many studies have suggested the existence of skin-specific a ntigens in rodents, but data in large-animal models are more limited. Methods. We have recently developed protocols for attaining stable mixed he matopoietic chimerism in miniature swine, using MHC-matched donors and reci pients, We have now assessed tolerance to donor-derived skin and cardiac al lografts in these chimeric animals, Results. Skin-graft rejection was seen in four of six animals receiving ski n grafts taken from the respective hematopoietic donors, In the other two a nimals, donor-derived skin grafts survived indefinitely. No cardiac-allogra ft rejection was observed in mixed-chimeric animals that received heart tra nsplants from their hematopoietic donors, even in animals that had already rejected skin allografts from the same donors. In all animals assessed, in vitro hyporesponsiveness to donor hematopoietic cells persisted. Conclusion, These findings support the concept that skin expresses immunoge nic alloantigens that either are not expressed or are not immunogenic in ca rdiac or hematopoietic tissue.