Immunohistochemical characterization of hepatic eosinophil cationic protein in primary biliary cirrhosis

We have previously reported that serum eosinophil cationic protein (ECP) levels are increased in primary biliary cirrhosis (PBC). However, little is known about the role of eosinophils in the pathogenesis of this disease. In this study, liver biopsy specimens obtained from 27 PBC patients (stage I: 11 cases; stage II: 9 cases; stage III: 5 cases; stage IV: 2 cases) were stained with a monoclonal antibody (EG2) produced against ECP in an attempt to elucidate whether EG2-positive eosinophils are involved in the destruction of bile duct in PBC. Needle liver biopsy specimens obtained from 24 patients with chronic hepatitis C (CHC) were used as controls. In PBC, more than 10 EG2-positive cells were noted per portal tract in 6 cases, less than 10 EG2-positive cells in 10 cases and none in 11 cases. In CHC, more than 10 EG2-positive cells were detected per portal tract in only one case, less than 10 EG2-positive cells in 3 cases and none in 20 cases. According to the semi-morphometric statistical analysis, the hepatic infiltration rate of EG2-positive activated eosinophils into the portal tract was significantly higher in PBC than in CHC. Based on the stages of PBC, the infiltration rate of EG2-positive cells was significantly higher in stages I and II than in stages III and IV. A significant correlation was found between EG2-positive cell infiltration and small round cell infiltration. These findings suggest that EG2-positive, activated eosinophils may be involved in the early stages of PBC when the inflammatory changes are localized in the portal tract. It is tentatively speculated that activated eosinophils may play a role possibly as effector cells in the immunopathogenesis of PBC.