Tolerized mice CD11c+ dendritic cells induce indoleamine 2,3-dioxygenase-dependent inhibition of type II collagen-specific T-cell proliferation. (a) Type II collagen (CII)-reactive CD4+ T cells (1 × 105/well) and irradiated antigen-presenting cells (APCs) (1 × 105/well) isolated from Peyer's patches of collagen-induced arthritis (CIA) mice were cultured with CD11c+ dendritic cells (DCs) (1 × 104/well) from tolerized mice or CIA mice in the presence or absence of CII (40 μg/ml) in 96-well, U-bottomed plates for 3 days. Some DCs were pretreated with 1-methyl tryptophan (1-MT) (200 μM) for 2 hours before coculture. Data presented as the mean counts per minute (cpm) of triplicate cultures. Values are the mean ± standard deviation from three independent experiments. *P < 0.05. (b) Cytokine concentrations in the coculture supernatants. Concentrations of IL-17, IL-10, and transforming growth factor beta (TGFβ) in the culture supernatants were measured by ELISA. Values are the mean ± standard deviation from three independent experiments. *P < 0.05, **P < 0.001.