Host mechanisms in viral hepatitis.

Hepatitis, a common human disease, may be followed by severe liver injury, eventually leading to fatty liver, liver fibrosis and hepatocellular carcinoma. CD8 T cells are a double-edged sword in the response to infection with the hepatitis virus. On one hand, rapid activation of CD8 T cells is critically important for the elimination of the virus. On the other hand, in persistent viral infection, the activation of CD8 T cells substantially contributes to liver injury. The clinical course of hepatitis, thus, critically depends on mechanisms regulating the activity of CD8 T cells. In observations in human hepatitis and in mice infected with the lymphocytic choriomeningitis virus, the clinical course of hepatitis is modified by several immunological factors including neutralizing antibodies: RIG-I, TLRs, MyD88, interferon type I, TNF-alpha, MHC I, Tap, TCR, CD8, IL-2, IL-7, PD-1, IFN-I, IL-10, IFN-gamma, perforins, serotonin and iNOS (table 1) . Additional experimental effort is needed to understand the concerted interplay of those molecules in viral hepatitis of man and mice.