IRF9 and infection: In addition to IFNAR1, we have also shown the importance of IRF9, a component of the IFN-I-induced signalling complex interferon-stimulated gene factor 3 (ISGF3), in functional T cell responses in LCMV-Arm-infection, with both IFNAR1 and IRF9 independently required in a CD8+ T cell-extrinsic manner [6].