Interferon regulatory factor 5(IRF-5) is a member of IRF family, which plays a critical role in the regulation of genes induced by viral infection, immunostimulation and cell growth regulation. The expression of IRF-5 is limited to lymphoid organs, dendritic cells, and peripheral blood lymphocytes, but is not expressed in numerous leukemia and lymphoma cell lines. Three IRFs(IRF-3, IRF-5, IRF-7) function as direct transducers of virus-mediated signaling and play a critical role in the expression of type I interferon genes and some chemokines.