Cytokeratin immunohistochemical examination of liver biopsies in infants with Alagille syndrome and biliary atresia.

Identifying bile duct epithelium is sometimes difficult with standard histologic techniques. The availability of antibodies to specific cytokeratin (CK) intermediate filaments has allowed identification of CK expressed by bile duct epithelium. Formalin-fixed, paraffin-embedded liver tissue from five infants (aged 1-12 months) with Alagille syndrome and five infants with biliary atresia (aged 1.5-11 months) were pepsin digested then reacted with a combination of anti-cytokeratin monoclonal antibodies using an avidin-biotin immunoperoxidase technique. Liver tissue obtained at autopsy from infants without primary liver disease (aged 22 weeks gestation to 24 months) was treated similarly for comparison. Control specimens showed progression from prominent immunoreactivity of the ductal plate cells at the rim of the portal tract (22-24 weeks gestation) to incorporation of tubular ductal structures into portal tract mesenchymal tissue (26-34 weeks gestation) and formation of intensely immunoreactive mature discrete interlobular ducts with progressive loss of cytokeratin immunoreactivity of the ductal plate cells (1-24 months). In contrast, biopsies from infants with Alagille syndrome showed few immunoreactive interlobular ducts. Biopsies from infants with Alagille syndrome less than 2 months old showed only immunoreactivity of single ductal plate cells or small ductules at the periphery of the portal tracts. Biopsies from some infants greater than 3 months old showed increased numbers of immunoreactive cells in groups and anastomosing bands lacking true lumens and extending into the fibrous bridges between adjacent portal areas (neoductular proliferation).(ABSTRACT TRUNCATED AT 250 WORDS)