[Immunology of hepatitis C: clinical significance of T cell response].

Hepatitis C virus (HCV) infection is a worldwide problem in terms of public health. It causes chronic hepatitis C in 60-80% of patients after acute hepatitis C. Chronic hepatitis C can progress to liver cirrhosis and hepatocellular carcinoma. In the present time, combination therapy of pegylated interferon-alpha and ribavirin is the standard therapy for hepatitis C, but it results in sustained virologic response only in 45-80% of treated patients. In addition, there is no available effective vaccine for HCV. To develop effective immunotherapy or preventive vaccine, understanding of the immune response against HCV is prerequisite. Among several components of immune system, T cells play a key role in the clearance of HCV and immunopathology during hepatitis C. In the study of HCV infection, however, the most important limiting factor is the absence of small animal model as only humans and chimpanzees can be infected by HCV. In this review, T cell response against HCV, which has been known from the studies of the HCV-infected patients and chimpanzees, will be discussed in several circumstances, including acute hepatitis C, chronic hepatitis C and recovered status from hepatitis C.