IDO in B-cell lymphoma lines and primary CLL cells. (A) Four B-cell lymphoma cell lines (Raji, Daudi, BJAB, and Jeko-1) and (C) 5 CLL patients’ PBMCs were cultured in the absence or presence of exogenous IFN-γ (50 U/mL) for 24 hours. Protein extracts were prepared for IDO western immunoblot analysis. Results are representative of 3 independent experiments. (B) IDO enzyme activity was evaluated by measuring the concentrations of l-tryptophan and l-kynurenine in the cell culture medium of the B-cell lymphoma lines using HPLC. Each bar represents the mean ± SD of the results from 3 independent experiments.