Indoleamine 2,3-dioxygenase-expressing CD11c+ dendritic cells display a phenotype consistent with the immature state. Indoleamine 2,3-dioxygenase (IDO)+CD11c+ dendritic cells (DCs) were stained for markers of DC maturity and were analyzed using three-color flow cytometry. Mononuclear cells from Peyer's patches were stained for CD11c, IDO, and Major Histocompatibility Complex (MHC) II, or costimulatory molecule markers. All plots were first gated on IDO+CD11c+ cells. Dotted line shows the isotype-matched controls. Data are the mean ± standard deviation of three experiments. MFI, mean fluorescence index.