Expression of IDO1 and IDO2 in CD123⁺/CCR6⁺ human DCs. (A) CD123⁺/CCR6⁺, nonadherent, immature human DCs (iDCs) or cytokine cocktail–matured DCs (mDCs¹² ) treated or not with IFN-γ (IFN DCs) were analyzed for IDO1 and IDO2 expression by RT-PCR. Water instead of cDNA served as negative and placenta cDNA as positive control. PCR products (β-actin: 407 bp, IDO1: 321 bp, IDO2: 371 bp) were separated on agarose gel. (B) iDCs were electroporated with water instead of siRNA (mock), control siRNA (CTR siRNA), or siRNA specific for IDO1 (IDO1 siRNA) and stimulated with a maturation cocktail and IFN-γ. IDO1 and IDO2 transcription was detected as described in panel A. (C) The relative expression level of IDO1 after siRNA treatment was analyzed by qRT-PCR. IDO1 expression levels of transfected DCs were correlated to iDCs (n = 7, mean value ± SD).