Interferon-γ acts directly on CD8+ T cells to increase their abundance during virus infection

Interferon-gamma (IFN gamma) is important in regulating the adaptive immune response, and most current evidence suggests that it exerts a negative (proapoptotic) effect on CD8(+) T cell responses. We have developed a novel technique of dual adoptive transfer, which allowed us to precisely compare, in normal mice, the in vivo antiviral responses of two T cell populations that differ only in their expression of the IFN gamma receptor. We use this technique to show that, contrary to expectations, IFN gamma strongly stimulates the development of CD8(+) T cell responses during an acute viral infection. The stimulatory effect is abrogated in T cells lacking the IFN gamma receptor, indicating that the cytokine acts directly upon CD8(+) T cells to increase their abundance during acute viral infection.