Interleukin-2 (IL-2) expression in livers of patients with chronic hepatitis C virus (HCV) infection

The studies performed till now have pointed to an increased serum levels of interleukin 2 (IL-2) in infection with hepatitis C virus (HCV). The present study was aimed at examining intrahepatic expression of IL-2 in children (n=15) and in adults (n=11) with chronic hepatitis C as well as its correlations with histological lesions and selected clinical data. The immunocytochemical techniques and in situ hybridization method were applied at light and electron microscopy level. Under the light microscope, expression of IL-2 was analysed semiquantitatively. As compared to the control material, in livers of both groups of chronic hepatitis C patients augmented expression of IL-2 was demonstrated. The reaction product was localized mainly in the cytoplasm of hepatocytes which was confirmed by hybridocytochemistry. The mean proportion of cells with positive reaction for IL-2 mRNA was significantly lower than the proportion of cells positive for the respective protein. No correlation was disclosed between IL-2 expression on one hand and grading or staging, alanine aminotransferase (ALT) and HCV RNA levels in serum on the other. At the ultrastructural level, IL-2 in hepatocytes was present mainly in the endoplasmic reticulum and mitochondria. Our studies have confirmed augmented expression of IL-2 in livers of patients with chronic hepatitis C and have demonstrated that hepatocytes represent the principal source of the cytokine in HCV in vivo infection. Moreover, expression of IL-2 in the infection was examined for the first time at the ultrastructural level. Mitochondrial localization of IL-2 suggests a direct involvement of the cytokine in disturbed function of the organelles.