Progressive liver injury in chronic hepatitis C infection correlates with increased intrahepatic expression of Th1-associated cytokines

Abstract

An imbalance between T helper cell (Th)1 and Th2-like cytokines has been described in several chronic infectious diseases. We therefore analyzed the intrahepatic messenger RNA (mRNA) expression of Th1-like (interleukin [1L]- 2, interferon [IFN]-γ) and Th2-like (IL-4, IL-10) cytokines in chronic hepatitis C patients (n = 17) and controls (n = 6) and correlated the results with liver histology and intrahepatic viral load. Intrahepatic cytokine mRNA and hepatitis C virus (HCV) RNA were quantitatively assessed by polymerase chain reaction (PCR) using a dot-blot hybridization technique. Liver biopsy specimens were histologically graded using the Scheuer Score. IFN-γ and IL- 2 mRNA expression were significantly upregulated in chronic HCV vs. controls (P < .002, P < .04, respectively). Both correlated significantly with histological fibrosis and portal tract inflammation. In contrast, the expression of IL-10 mRNA was decreased in cirrhosis and chronic HCV compared with controls (P < .02, P < .0001, respectively). IL-4 mRNA was detected inconsistently at low levels in all groups. Intrahepatic viral load did not correlate with either cytokine expression or tissue injury. In conclusion, the progressive liver injury seen in chronic HCV is associated with the upregulation of intrahepatic Th1-like cytokines and the down-regulation of IL-10, a Th2-like cytokine. These results suggest a role for delayed-type hypersensitivity immune reactions in HCV related liver injury.