A functional model of hepatocyte transplantation for in vivo immunologic studies

Background. Previous studies to determine the significant donor and host factors which contribute to immune responses to allogeneic hepatocytes have been pursued with in vitro and in vivo studies. However, in order to further characterize in vivo host immune responses to transplanted hepatocytes in conjunction with their consequences upon allograft survival, a functional model of hepatocyte transplantation in which the function and survival of transplanted hepatocytes could be serially assessed was pursued. Methods. A transgenic mouse line expressing the human α₁-antitrypsin (hA1AT) gene was developed in an FVB/N (H2(q)) mouse (hA1AT-FVN/N). Hepatocytes from these 'donor' transgenic mice were transplanted into host mice by intrasplenic injection, and subsequent survival of the transgenic hepatocytes was determined by assay for the secreted hA1AT protein in host serum by enzyme- linked immunosorbent assay. Results. Transplantation of transgenic 'donor' hepatocytes (hA1AT-FVB/N) into (a) syngeneic FVB/N (H2(q)), (b) allogeneic immunoincompetent C57BL/6.SCID (H2^b), or (c) allogeneic T cell-deficient (outbred) hosts resulted in long-term survival (> 16 weeks) of hepatocytes. Transplantation of allogeneic hepatocytes (hA1AT-FVB/N, H2(q)) into C57BL/6 (H2^b), C3H (H2(k)), or BALB/c (H2(d)) hosts resulted in loss of hA1AT in host serum by day 10 after transplant. Likewise, transplantation of allogeneic hepatocytes into hosts deficient in B cells, CD8⁺ T cells, or CD4⁺ T cells resulted in loss of hA1AT by day 10 after transplant. Conclusions. This functional model of hepatocyte transplantation is validated for the study of host immune responses to hepatocellular grafts and to assess efficacy of strategies designed to alter these in vivo immune responses. The immunologic rejection of allogeneic hepatocytes appears to be T cell- mediated.