Characterization of maturation status and IDO competence in human monocyte-derived DCs activated with LPS with or without IFN-γ for different time periods. (A) DCs after activation with LPS only or LPS in combination with IFN-γ for different time periods were examined for the expression of cell-surface molecules of DCs typically associated with maturation (shaded histograms indicate isotype control; open histograms, DCs after activation). One representative of 10 similar experiments is shown. (B top) IDO protein expression in differently activated DCs was examined by immunoblot analysis; (bottom) the concentrations of tryptophan (TRP; ▩; left scale) and kynurenine (KYN; ■; right scale) in cell culture supernatants of the differently activated DCs were determined at the termination of the activation period. Results of 1 of 10 similar experiments are shown. (C) The concentrations of TRP and of KYN were examined as in panel B in cell culture supernatants 24 hours (top) and 48 hours (bottom) after removal of the activating agents and reculture in fresh medium. Results of 1 experiment, representative of 10 experiments, are shown; **P < .01; n.s. indicates not significant.