Effects of IDO knockdown on DCs. DCs were cultured in medium alone (control) or transfected with control siRNA (Ctrl siRNA), siRNA 339, siRNA 620, or siRNA 890 for 6 h, followed by stimulation with ES antigen for 24 h. (A) Relative IDO mRNA expression (normalized to GAPDH) was quantified by real-time qRT-PCR. ***p < 0.001. (B) IDO protein levels were analyzed by Western blotting.