Primary biliary cirrhosis (PBC): antigen-presenting cells differ in their distribution in early and late stage PBC and involve the ductal, but not the ductular compartment.

We have studied the distribution patterns of antigen-presenting cells (APCs) in different stages of primary biliary cirrhosis (PBC). 58% of cases with early PBC (stages I and II) exhibited dendritic APCs (S-100+, HLA-DR+, KiMlp+) in bile duct epithelia. In contrast, APCs, were not detected in ductular proliferations occurring in late PBC (stages III and IV), but occurred in portal tracts and piecemeal necroses. There was a correlation between the presence of APCs and HLA-DR expression in bile ducts but, in contrast to former studies, we noted a heterogeneous ductal HLA expression. These observations support the hypothesis that: 1) APC distribution in PBC may change as a function of stage, involving hepatic parenchyma in late PBC; 2) ductular epithelia may not represent a target for immune attack, because APCs do not accumulate in these structures; and 3) HLA expression in bile ducts may be heterogeneous, suggesting one mechanism why bile duct destruction in PBC does not take place in a synchronous way.