Kinetics of IDO and IFN-γ mRNA expression by human PBMCs after CTLA-4-Fc and CD28-Fc treatment. IDO (A) and IFN-γ (B) mRNA expression were analyzed using real-time PCR on untreated PBMCs (▵) and PBMCs treated with CTLA-4-Fc (□) or CD28-Fc (⋄). *P values less than .05 are based on 5 independent experiments. Mean values plus standard errors are shown.