Type I interferon-stimulated gene (ISG) that plays a critical role in antiviral and antibacterial activity (PubMed:34722780). During bacterial infection, promotes macrophage differentiation and facilitates inflammatory cytokine secretion (PubMed:34722780). Plays a role in the control of respiratory syncytial virus/RSV infection, reducing the ability of the virus to replicate (PubMed:32611756). Exhibits a low antiviral activity against hepatitis C virus (PubMed:21478870). Acts also as a feedback regulator of IFN responses by negatively regulating IKBKB and IKBKE kinase activities through interaction with FKBP5 (PubMed:31434731). Interacts with FKBP5; this interaction modulates IKBKB and IKBKE kinase activities. By type I interferons (PubMed:21478870). By M. tuberculosis infection (PubMed:34722780). Belongs to the IFI44 family.