AASLD Abstracts (pp. 179A–281A)
Journal: Hepatology (2003)

Background: Hepatocellular carcinoma (HCC) occurs after many years of chronic viral hepatitis.In support of this notion, we have investigated that chronic immune-mediated liver cell injury triggers the development of HCC in the absence of cofactors such as viral transactivation, insertional mutagenesis and genotoxic chemicals in a hepatitis B virus (HBV) transgenic mouse model.Recently, we have reported that Fas ligand (FasL)-induced pathogenetic events are critically involved in the process of hepatocarcinogenesis (J Exp Med 196:1105,2002).While FasL is known to be expressed on activated T lymphocytes, the molecular and cellular mechanisms potentially responsible for HCC development are not well defined.In the current study, we asked the relative procarcinogenic effects of lymphocyte subsets, CD4+, CD8+ T cells and B cells, in the model of chronic immune-mediated hepatitis.Methods: Since HBV transgenic mice are immunologically tolerant to hepatitis B surface antigen (HBsAg) and develop no evidence of liver disease, three-month-old transgenic mice were thymectomized, bone marrow-reconstituted and adoptively transferred with CD4+, CD8+ T cell and B cell enriched or depleted splenocytes obtained from HBsAg-primed, syngeneic nontransgenic donors by complement fixation using the specific monoclonal antibodies.The resultant liver disease was monitored histologically and biochemically, as serum alanine aminotransferase (SALT) activity.Hepatocyte apoptosis was evaluated immunohistochemically using monoclonal antibody specific for the activated form of caspase-3 and by TUNEL assay.Hepatocyte regeneration was detected by staining for proliferating cell nuclear antigen (PCNA).Results: As shown in the table, CDW enriched, HBsAg-primed splenocyte transfer caused severe and prolonged disease kinetics.12 out of the 14 mice in this group that were sacrificed at > 14 months of age displayed several large liver tumors which were histologically consistent with HCC, comparable to the mice transferred with total splenocytes except for the peak SALT at 7 days after adoptive transfer.In contrast, CD4+ enriched cell transfer demonstrated lower levels of liver disease and developed diminished incidence of HCC (4 of 17).However, the numbers and sizes of tumors were comparable among the mice complicated with HCC following the transfer with total splenocytes and with T cell subsets.Consistent with the difference in disease activity, immunohistochemical analysis revealed marked increase in the numbers of activated caspase-3+, TUNEL+ and PCNA+ hepatocytes in the mice transferred with CD8+ enriched splenocytes, and they were largely diminished following CD4+ enriched cell transfer.B cell depletion had no effect on disease kinetics in this model.Unmanipulated transgenic mice developed neither liver cell injury nor HCC.Conclusions: The results indicate that CD8+ T cell subset is primarily responsible for the induction of prolonged hepatitis that sets up a cycle of liver cell destruction and regeneration which greatly increases the incidence of HCC in the HBV transgenic mouse model.Furthermore, the current experiments suggest that the pathogenetic events induced by individual T cell subsets exert the differential procarcinogenic potential especially in the initiation stage rather than the promotion stage of hepatocarcinogenesis. Liver Dkeesc and HCC Devdopmsat Folkwine immune Cell Subset Tramhr SALT Ac(ivih.iUQ Splenocyte lrsmter