Normal development in porcine thymus grafts and specific tolerance of human T cells to porcine donor MHC

The induction of T cell tolerance is likely to play an essential role in su ccessful xenotransplantation in humans. In this study, we show that porcine thymus grafts in immunodeficient mice support normal development of polycl onal, functional human T cells. These T cells were specifically tolerant to MBC Ags of the porcine thymus donor and responded to nondonor porcine xeno antigens and alloantigens, Exogenous IL-2 did not abolish tolerance, sugges ting central clonal deletion rather than anergy as the likely tolerance mec hanism, Our study suggests that the thymic transplantation approach to achi eving tolerance with restoration of immunocompetence may be applicable to x enotransplantation of pig tissues to humans.