Type I IFN signaling facilitates the development of IL-10-producing effector CD8 T cells during murine influenza virus infection.

Recent evidence has suggested that IL-10-producing effector CD8 T cells play an important role in regulating excessive inflammation during acute viral infections. However, the cellular and molecular cues regulating the development of IL-10-producing effector CD8 T cells are not completely defined. Here, we show that type I interferons (IFNs) are required for the development of IL-10-producing effector CD8 T cells during influenza virus infection in mice. We find that type I IFNs can enhance IL-27 production by lung APCs, thereby facilitating IL-10-producing CD8 T-cell development through a CD8 T-cell-nonautonomous way. Surprisingly, we also demonstrate that direct type I IFN signaling in CD8 T cells is required for the maximal generation of IL-10-producing CD8 T cells. Type I IFN signaling in CD8 T cells, in cooperation with IL-27 and IL-2 signaling, promotes and sustains the expression of IFN regulatory factor 4 (IRF4) and B-lymphocyte-induced maturation protein-1 (Blimp-1), two transcription factors required for the production of IL-10 by effector CD8 T cells. Our data reveal a critical role of the innate antiviral effector cytokines in regulating the production of a regulatory cytokine by effector CD8 T cells during respiratory virus infection.