Examination of serum class I antigen in liver-transplanted rats.

We examined the appearance of donor (DA) type class I antigen in the serum of rats that had received isogeneic (DA----DA) or allogeneic (DA----PVG, DA----BN, DA----LEW) liver transplants with or without cyclosporin A treatment, using two-site enzyme immunoassay. We also tested the serum titre of class I antigen in the normal DA rats with either 70% hepatectomy or cyclosporin A treatment, in order to clarify the relationship between the fluctuation in the serum titre of class I antigen in the recipient and the outcome of the transplanted liver graft. The suppression of liver graft rejection by cyclosporin A treatment significantly lowered the serum level of donor liver-derived class I antigen as compared with that of the recipient without cyclosporin A for a certain period. However, there was almost no correlation between the intensity of rejection of the liver graft and the serum level type class I among these allogeneic rejection and non-rejection liver transplantation combinations. The amount of donor-type class I antigen in the recipient's serum is dependent on whether the grafted liver is severely damaged following partial hepatectomy, whether the liver has associated biliary complications or ischaemic damage, or whether the liver has had absolute residual parenchymal cell volume or function following liver rejection. Our results suggest that the appearance of donor type class I antigen following liver transplantation is dependent on many factors, and therefore the titre of serum class 1 antigen may not always be a decisive indicator of liver graft rejection.