— Peripheral blood lymphocyte subsets involved in cytotoxicity to autologous hepatocytes have been characterized by isolation on antibody-coated Petri dishes in autoimmune and HBsAg-positive chronic active hepatitis (CAH). In autoimmune CAH and in HBsAg-positive CAH without HBcAg in liver tissue, cytotoxicity is sustained by non-T lymphocytes and is confined to M1-positive cells bearing Fc receptors: M1 cytotoxicity inhibition by adding aggregated IgG suggests that these cells are responsible for an antibody-dependent cell-mediated mechanism (ADCC). Moreover, when T-enriched fractions were separated in T4, T8 and 5/9 positive subsets, only the first one showed a significant cytotoxicity: T4 positive cells might act as cytotoxic T cells or might be involved in delayed type hypersensitivity (DTH) reactions. Cytotoxic T lymphocytes in HBsAg-positive CAH with HBcAg in liver tissue are confined in T8 positive subset, while helper/inducer T cells (T4 positive or 5/9 positive) seem to play an important role only in the induction of cell-mediated injury against hepatocytes. The inhibition of T cell-cytotoxicity by preincubating liver cells with monoclonal antibody (Mab) anti-HLA AB and not with Mab anti-HLA DR or aggregated IgG supports the involvement of the class I major histocompatibility complex (MHC) expressed on the hepatocyte surface.
