Subcellular localization of IRFs and MyD88. (a) Confocal images of HEK293T cells transiently expressing IRF-3YFP, IRF-7YFP, MyD88CFP, or TRIFCFP. (b) Confocal images of HEK293T cells coexpressing MyD88CFP with IRF-3YFP or IRF-7YFP. (c) HeLa cells were transfected with expression plasmids for IRF-7YFP or IRF-3YFP and MyD88CFP. FRET, YFP, and CFP images were collected by using an inverted fluorescence microscope equipped with a cooled charge-coupled device camera. FRETC was determined as described in the text and presented in the pseudocolor mode as indicated below the photographs.