Cytotoxic T lymphocytes derived from patients with chronic hepatitis C virus infection kill bystander cells via Fas-FasL interaction.

The role of Fas-mediated lysis of hepatocytes in hepatitis C virus (HCV)-induced injury is frequently discussed. We therefore analyzed the effect of the number of HCV antigen-expressing cells, the mode of antigen presentation, and the number of cytotoxic T lymphocytes in a coculture system mimicking cellular components of the liver. Here, we show that endogenously processed HCV proteins are capable of inducing bystander killing. We further demonstrate that 0.8 to 1.5% of cells presenting HCV antigens suffice to induce lysis of 10 to 29% of bystander cells, suggesting that the mechanism may be operative at low fractions of infected versus uninfected hepatocytes in vivo. Our data underscore the role of the Fas pathway in HCV-related liver injury and support the exploration of Fas-based treatment strategies for patients with chronic hepatitis C virus infection.