| Abstract: | Spontaneous tolerance of liver allografts can be observed in inbred rats. In order to study the influence of the density of major histocompatibility complex alloantigens on the fate of liver allografts in the rat, liver allografts were performed in a semi-allogeneic and a fully allogeneic combination. Comparisons of the fate of heart and kidney allografts were made in the same combinations. A similar proportion of spontaneously tolerated liver allografts was observed in the two combinations; after a few months these animals were in a state of donor-specific unresponsiveness. A spontaneous prolongation of kidney allografts was observed only in the semi-allogeneic combination. These animals were not in a state of donor-specific unresponsiveness. These results suggest that induction of liver allograft tolerance in the rat is not decisively influenced by the importance of the density of major histocompatibility complex antigens present on the graft and that its mechanism may be different from that which causes spontaneous prolongation of semi-allogeneic kidney allografts. |
