Florid duct lesion in primary biliary cirrhosis shows highly proliferative activities

Primary biliary cirrhosis is characterized by non-suppurative inflammation and destruction of the interlobular bile ducts (IBDs) (florid duct lesions). The present study attempted to analyze the cell kinetics of florid duct lesions using the histometry, immunostaining of proliferating cell nuclear antigen and by counting argyrophilic nucleolar organizer regions. Florid duct lesions disclosed nuclear stratification, pseudopapillary infoldings and tortuosity. These findings suggest increased proliferative activity of epithelial cells in these affected ducts. Proportion of proliferating cell nuclear antigen positive interlobular bile ducts (88.8 +/- 7.9%) and counts of argyrophilic nucleolar organizer regions in biliary epithelial cells (3.89 +/- 0.73) were increased in florid duct lesions relative to non-inflamed interlobular bile ducts (45.0 +/- 25.4% and 2.65 +/- 0.67, respectively) in primary biliary cirrhosis and also relative to interlobular bile ducts (21.8 +/- 8.6% and 2.25 +/- 0.09, respectively) in normal livers, which supports the above-mentioned suggestion. The increased outer diameter of these affected bile ducts which was demonstrated histometrically, may be due to biliary epithelial proliferation with variable luminal dilatation. The present study showed that an increased proliferative activity of biliary epithelial cells is one of the characteristics of florid duct lesions and results in an increase in the size of the affected bile ducts. It remains unclear, however, why proliferation and extensive destruction of biliary epithelial cells coexist in primary biliary cirrhosis.