Interferons (IFN)s are involved in a multitude of immune interactions during viral infections and play a major role in both the induction and regulation of innate and adaptive antiviral mechanisms. During infection, host-virus interactions signal downstream molecules such as transcription factors such as IFN regulatory factor-3 (IRF3) which can act to stimulate transcription of IFN-alpha/beta genes. Unlike IRF3, IRF8 appears to act as a negative regulator of IFN-induced genes in most cases, but IRF8 mediates activation of NF-κB by the toll-like receptor 9 (TLR9) after stimulation by unmethylated CpG DNA in dendritic cells. Finally, it has been shown that IRF8 decreases bcl-2 expression and thus may play a role in chronic myelogenous leukemia.