Protective and Pathogenic T Cell Responses to Virus Infections

T cells play a key role in viral pathogenesis. By killing infected cells and secreting antiviral cytokines, effector T cells that have reached infection sites are major contributors to viral clearance as well as tissue immunopathology. Both T cell-defensive and -destructive functions are perhaps best epitomized during hepatotropic viral infections in susceptible hosts. Using hepatitis B virus infection as a paradigmatic example, we will review here our current understanding of how effector T cells migrate to infected tissues and perform protective and pathogenic effector functions.