New Insight into Immunopathology of Viral B and C Hepatitis

Overview

The interaction of non-cythopatic, hepatotropic viruses of hepatitis B and C with the host’s immune system playsa critical role in determining the viral clearance and it contributes to the liver damage. The initial line of defence isantigen non-specific and is mediated by natural killer cells and macrophages. Simultaneously, virus-specificimmunity is induced by professional antigen presenting cells that process and present viral antigens to T and Blymphocytes in the regional lymph nodes. Thereafter, viral specific T helper cells are activated and these cells initiatethe anti-viral immune responses of B and CTL lymphocytes. Early, multispecific T cell responses are associatedwith viral clearance, whereas the imbalance of viral specific Th1 and Th2 lymphocytes plays a crucial role in theviral persistence. The imbalance of viral specific Th1 and Th2 lymphocytes leads to inadequate activation of antigenspecific CTL cells. After recognition of viral antigens, T helper lymphocytes are differentiated to Th1 and Th2 cellsaccording to the type of secreted cytokines. Th1 cells produce cytokines: interleukin-2, IFN-γ, TNF-α, which areresponsible for effective activation of CTL cells. In contrast, interleukin-4, interleukin-5 and interleukin-10 aresecreted by Th2 cells, which are involved in activation of B lymphocytes and in production of neutralizing antibodies.These finding suggests that the viral clearance is associated with the early development and adequate mounting ofthe anti-viral multispecific immune responses of T helper and cytotoxic T lymphocytes.

Key words:
immunopathology, hepatitis B, hepatitis C, immune response, viral clearance.