Infection with lymphocytic choriomeningitis virus is associated with marked polyclonal activation of the CD8+ T cell subpopulation. In this report the cytokine production of virus-activated T cells is analyzed and the producing cell subset is characterized phenotypically. Coinciding with other parameters of cell-mediated immunity, splenic T cells appear which are able to release high amounts of IFN- gamma, but not IL-5, IL-10 or tumor necrosis factor-alpha upon short-term stimulation with anti-CD3 in vitro. A similar profile is observed analyzing T cells taken from an inflammatory site. Phenotypically, the main cytokine-producing cell subset is found to be CD8+ cells targeted for homing to inflammatory sites (VLA-4hiL-selectinlo) of which 30-40% were positive by intracellular staining for IFN-gamma. This subset also contains all T cells with a cytotoxic potential as measured by redirected killing. An enhanced cytotoxic potential as well as an increased capacity to produce IFN-gamma is observed for at least 2 months after infection and cell sorting analysis revealed that this could be ascribed to a long-standing increase in the frequency of CD8+ Pgp-1hi cells. Therefore, these results demonstrate that systemic virus infection may exert marked perturbation of the CD8+ T cell population resulting in generation of a long-lived subset of primed cells with important effector potential.