Differences between pig tissues in the expression of major transplantation antigens: possible relevance for organ allografts

Evidence is presented that there are differences between pig liver and kidney parenchymal cells in the expression of major histocompatibility complex antigens. Analogues of I-region antigens of the mouse are detectable on kidney cells and some peripheral blood leukocytes (PBL) but not on liver, platelets, and other PBL. Such differences between liver and kidney may explain (a) the fate of these organs as allografts and (b) the donor-specific protection of kidney by liver. Other antigens peculiar to skin and kidney have been detected but require further characterization.