ABSTRACT
Cytokines play an important role in the defense against viral infections, both indirectly,
through determination of the predominant pattern of host response, and directly, through
inhibition of viral replication. However, in the context of an inflammatory response
against a virus, cytokines may also lead to liver damage. The importance of this is
best demonstrated in hepatitis B virus (HBV). In acute HBV infection, a vigorous polyclonal
cellular immune response is critical; thus type 1 cytokine release is essential to
initiating an effective immune response. The cytokines released by CD4+ and CD8+ cells also play an important role in downregulation of HBV replication, demonstrating
that it is possible to control a viral infection without the death of infected cells.
However, if there is a defect in the acute response, HBV becomes chronic; in that
case, the presence of an ongoing suboptimal inflammatory response can activate the
process of hepatic fibrosis. In hepatitis C infection, the role of cellular immune
responses and cytokines is less clear. Hepatitis C may be resistant to inhibition
by cytokines, so cytokines may have a more prominent role in liver damage than in
controlling viral replication. Both hepatitis B and C may have specific mechanisms
to inhibit cytokine production, highlighting the critical role of these molecules
in recovery from infection.
KEY WORDS
cytokines - hepatitis B - hepatitis C
