Immunohistochemical characterization of inflammatory infiltrates in primary biliary cirrhosis

Ten liver biopsy specimens from nine patients with PBC stages II to IV were studied immunohistochemically with a broad panel of monoclonal antibodies. In areas of bile-duct proliferation, many BA1+ B-lymphocytes and OKT4+/Leu3a+ helper/inducer T-cells were observed, admixed with some C3b-receptor positive, mono- and polymorphonuclear OKM1+ cells. Numerous IgM-containing plasma cells were seen in portal tracts showing bile-duct proliferation. In contrast, areas of piecemeal necrosis and intralobular spotty necrosis consisted mainly of OKT4+/Leu3a+ helper/inducer, and OKT8+ suppressor/cytotoxic T-cells, admixed with some OKM1+ polymorphonuclear granulocytes. Almost no BA1+ B-lymphocytes or Ig-containing plasma cells were observed in areas of piecemeal necrosis and spotty necrosis. Major histocompatibility complex (MHC)-class I antigens (i.e. HLA-A,B,C) were demonstrated either on the liver cell membrane, or on sinusoidal lining cells. The latter also expressed MHC-class II antigens (i.e. HLA-DR). In two liver biopsies, an increased expression of HLA antigens was observed near areas of piecemeal and spotty necrosis. Our results indicate that several immune mechanisms each with a particular topographical distribution, are operative in PBC. Inflammatory cells, involved in humoral immunity, are present mainly in areas of bile duct proliferation. In contrast, the effector cells of antigen-specific cellular cytotoxicity are present in areas of piecemeal necrosis and spotty necrosis. In the latter areas, a pronounced expression of MHC products representing the afferent limb of the cell-mediated immune response, may permit an optimal T-cell-mediated immune effect or, eventually, result in adverse effects.