IRF8 contributes to the rapid expression of IFN-β. (A) 32Dcl3 cells were transfected with IRF8 plasmid. IRF8 protein levels in total cell lysates by Western blot. Similar results were obtained in 3 independent experiments, one of which is shown. (B) Reintroduction of IRF8 into 32Dcl3 (IRF8^−/−) cells. IFN-β transcription in cells stimulated with Sendai virus for 2 hours, as determined by real-time PCR. (C) WT and mutant IRF8 activate expression of a luciferase reporter construct driven by the IFN-β promoter region in 32Dcl3 cells induced by Sendai virus after 2 hours. A schematic representation of IRF8 mutant constructs is shown on the left. The DBD and IAD are highlighted. Luciferase activity of the respective constructs is shown in the graph on the right. (B-C) Data are mean ± SD from 3 independent experiments.