Donor class I and class II major histocompatibility complex antigen expression following liver allografting in rejecting and nonrejecting rat strain combinations.

Orthotopic liver allografts in the nonrejecting DA-to-PVG strain combination and in the DA-to-LEW strain combination were studied at various times after transplantation for donor class I and class II MHC expression using immunohistological techniques and quantitative analyses. DA-to-DA isografts were also studied. In the isografts, weak class I induction on hepatocytes and biliary epithelium was noted from day 5, and this persisted to day 15, the last time point examined. In DA-to-PVG allografts, class I induction also appeared on hepatocytes and biliary epithelium from day 5, but was more intense than in the isografts. Nevertheless, the induction was patchy within most grafts, and in some grafts was not prominent. Quantitative absorption analyses demonstrated that the maximum increase in donor class I expression was only 3-fold over the normal liver. In the strong DA-to-LEW combination, class I induction on hepatocytes seemed to appear earlier, beginning at day 3, and was more uniform and intense than in the DA-to-PVG model from day 5. In the isografts, there was no induction of class II antigens on hepatocytes or biliary epithelium at any stage, but from days 5 to 15 there was a marked increase in the number of isolated, class II-positive cells in the hepatic lobule, probably representing class II induction in the Kupffer cells of the isografts. In DA-to-PVG allografts, biliary epithelium became class II-positive from day 5, and this persisted to day 30, the last time point examined. Weak but definite class II induction was seen on some hepatocytes from day 5 through day 30. However, the majority of hepatocytes remained class II-negative. By day 30, there was virtually no donor class II staining the sinusoids, but isolated class II-positive cells of recipient type were seen, the pattern suggesting a replacement of the graft Kupffer cells by recipient Kupffer cells at this stage. By quantitative absorption analysis, donor class II expression in the grafts increased approximately 5-fold. In DA-to-LEW allografts, class II induction was not noticeably different from that seen in the DA-to-PVG model, except that induction of class II antigens on the Kupffer cells possibly appeared earlier in this strain combination.