Interferons (IFN) exert their multiple biological effects through the induction of expression of over 30 genes encoding proteins with antiviral, antiproliferative and immunomodulatory functions. Among the many IFN-inducible proteins are the Interferon Regulatory Factors (IRFs), a family of transcription regulators, originally consisting of the well-characterized IRF-1 and IRF-2 proteins; the family has now expanded to over 10 members and is still growing. The present review provides a detailed description of recently characterized IRF family members. Studies analyzing IRF-expressing cell lines and IRF knockout mice reveal that each member of the IRF family exerts distinct roles in biological processes such as pathogen response, cytokine signalling, cell growth regulation and hematopoietic development. Understanding the molecular mechanisms by which the IRFs affect these important cellular events and IFN expression will contribute to a greater understanding of events leading to various viral, immune and malignant disease states and will suggest novel strategies for antiviral and immune modulatory therapy.
