For example, in chronic HBV and HCV infection, although the viruses themselves are not cytopathogenic, activated CD8+ T cells kill viral infected hepatocytes, while activation of CD4+ T cells produces inflammatory cytokines and intern controls CD8+ T cell cytotoxicity contributing to the progression of liver disease (Rehermann, 2000; Rosen et al., 2002; Chang, 2003). The gene discussed is CD8A; the disease is liver disorder.