SPECIFIC TOLERANCE ACROSS A DISCORDANT XENOGENEIC TRANSPLANTATION BARRIER

Successful induction of tolerance across disparate (discordant) specie s barriers could overcome the organ shortage that presently limits cli nical transplantation. We demonstrate here that xenogeneic swine thymi c transplants can induce tolerance to swine antigens in mice, while po sitively selecting functional host CD4(+) T cells. Immunologically nor mal C57BL/10 mice were thymectomized and depleted of T and natural kil ler cells; then they received transplants of fetal pig thymus and live r fragments. Mature mouse CD4(+) T cells developed in the pig thymus g rafts and migrated to the periphery. Swine grafts grew markedly and no anti-pig IgG response was produced. Mixed lymphocyte reactions confir med that the new T cells were functional and were tolerant to pig anti gens.