Liver graft induced donor specific unresponsiveness without class I and/or class II antigen differences.

L IVER allografting induces specific systemic unresponsiveness to subsequent other donor tissues in pigs. l rats,2 and mice.3..Although the mechanism remains unclear, soluble donor crass I major histocompatibility complex (MHC) antigens and/or anti-donor class II alloantibodies have been proposed as critical components of the induced unresponsiveness.2.4.5 If those explanations are correct, a liver graft should not be able to protect extrahepatic tissues if one or both of these potential mechanisms are inoperative. In the present study, the induction of unresponsiveness by liver allografts was observed in mouse strain combinations where there was class I MHC mismatching only (B lOAKM--+B lOBR, absence of anti-donor class II antibodies), class II MHC mismatching only (ATH~ATL, absence of class I alloantigens), and only minor histocompatibility complex (mHC) mismatching (B lOBR ~ C3H, absence of both class I and class II alloantigens). The results offered a perspective about the role of factors other than soluble class I antigens and class II antibodies in explaining the mechanisms of liver allograft-induced tolerance.