IRF5 is a member of the interferon regulatory factor (IRF) family, a group of transcription factors with diverse roles, including virus-mediated activation of interferon, and modulation of cell growth, differentiation, apoptosis, and immune system activity. Members of the IRF family are characterized by a conserved N-terminal DNA-binding domain containing tryptophan (W) repeats. Multiple transcript variants encoding different isoforms have been found for this gene, and a 30-nt indel polymorphism Recombinant human IRF5 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.