[Spontaneous tolerance of liver allograft in the rat (author's transl)]

Several clinical and experimental arguments suggest that the liver has a privileged status regarding allograft rejection. The purpose of our study in inbred rats was to verify this notion in animals with precise histocompatibility relationships. Non auxiliary heterotopic liver transplantation, in which the graft ensures totally the hepatic function of the recipient, is equivalent in this view to orthotopic liver transplantation but has the major advantage to permit more easily the obtention of a low operative mortality. We compared the rejection of heterotopic heart allografts and heterotopic non auxiliary liver allografts in two semi-allogeneic donor-recipient combinations on inbred rats. Our main finding was that, contrasting with the constant acute rejection of heart allografts, about one-third of liver allografts were spontaneously tolerated. Test skin and heart allografts performed in rats with spontaneously tolerated liver allografts suggested that these animals were in a state of donor-specific non responsiveness. Spontaneous tolerance of organ allografts is very uncommon and our observation with liver allografts in inbred rats reinforce the concept that the liver has a privileged status facing rejection.