HCV is thought to be a non-cytopathic virus and liver damage is probably immune mediated. The large majority of infected individuals exposed to HCV become chronically infected although the mechanisms underlying this high rate of chronicity are not known. Neutralizing antibodies to HCV can be detected in serum and T-helper (CD4) lymphocytes responsive to both structural and non-structural HCV proteins can often be detected in patients with chronic HCV infection.
Cytotoxic T lymphocytes (CTLs) are thought to be particularly important in viral pathogenesis as they recognize viral antigens on cell surfaces in conjunction with major histocompatibility complex (MHC) class I proteins and lyse infected target cells.
Progression of liver disease due to HCV is marked by prog-ressive increases in hepatic fibrosis associated with activation of hepatic stellate cells, presumably through cytokine mediators produced as part of the immune response to HCV.