IRF9 and bacterial infectious disease: In addition, a further 12 ISGs of 380 tested ISGs including STAT1, STAT2, JAK1, IRF9, IRF2, IRF7 are key elements of IFN signaling, and classical and well-known ISGs such as ISG15, PKR, MX1, IFIT1, PML, IFI27 play key roles in viral or bacterial infections [11].