Role of T lymphocytes and natural killer cells in pathogenesis of chronic viral hepatitis

Hepatitis B (HBV) and C (HCV) viruses are unique because of their massive capacity to establish persistent infection, cirrhosis, and liver cancer. In spite of differences in their genome organization, life cycles and replication strategies, HBV and HCV have same features, such as noncytopathic nature and also the potential to induce chronic liver disease. It is suggested that immunologically mediated processes play a key role in the pathogenesis and outcome of these infections. Nevertheless, the rate of disease progression from chronic phase to cirrhosis varies considerably among infected patients, and the factors that regulate it are greatly unknown.Natural killer (NK) cells display the major effectors population of the innate immune system and are abundant in the human liver tissue. Recently, it has been suggested that NK cells not only exert antiviral functions but may also regulate adaptive immune responses by deletion of virus-specific CD8 T cells.
In present study, we have reviewed current knowledge of the roles of immune cells in the pathogenesis of chronic hepatitis B and C, and have discussed recent discoveries that introduce natural killer cells as regulators of T cell function and liver inflammation.