Histological and immunohistochemical study of the gall bladder lesion in primary sclerosing cholangitis.

The histological features and type of mononuclear cell infiltrate in gall bladders from six patients with primary sclerosing cholangitis were studied using routine staining techniques and immunohistochemistry. Control studies were performed using the gall bladders from six patients (age and sex matched) with chronic cholecystitis and four with primary biliary cirrhosis. A range of histological abnormalities was present in gall bladders from patients with primary sclerosing cholangitis including a mild to moderate degree of epithelial hyperplasia, pseudogland formation, and mononuclear cell infiltrate of the epithelium; moderate to severe chronic inflammatory cell infiltrate and fibrosis affecting the superficial and deep layers of the gall bladder wall; and minimal smooth muscle hypertrophy. These abnormalities were non-specific and were also present in gall bladders from patients with chronic cholecystitis and primary biliary cirrhosis. Vasculitis and granulomas were not present in the patients with primary sclerosing cholangitis. Immunohistochemistry showed that the superficial and deep mononuclear cell infiltrate in primary sclerosing cholangitis gall bladders was composed predominantly of lymphocytes, in contrast to chronic cholecystitis where macrophages were found in similar or greater numbers. Moreover, T lymphocytes (activated and resting) were present throughout the lymphocytic infiltrate and were apposed to the base and interdigitated between the biliary epithelial cells in significantly greater numbers than in chronic cholecystitis gall bladders. B lymphocytes were present only in lymphoid follicles. Comparative studies using liver biopsy specimens from three of the primary sclerosing cholangitis patients showed a similar T lymphocyte portal tract infiltrate. We conclude that a number of non-specific chronic inflammatory histological abnormalities were present in primary sclerosing cholangitis gall bladders. Immunohistochemistry found other features that were present in this disease - a predominantly lymphocytic mononuclear cell infiltrate of the superficial and deep layers of the gall bladder wall and the presence of T lymphocytes that infiltrated the biliary epithelial cells. These findings support the hypothesis that aberrant cell mediated immune mechanisms may play a role in the pathogenesis of both the intrahepatic and extrahepatic lesions in primary sclerosing cholangitis.