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. 2012 Sep 13;7(9):e44797. doi: 10.1371/journal.pone.0044797

Figure 5. Impact of tryptophan contamination in 1-L-MT on kynurenine detection and determination of IDO activity.

Figure 5

(A) Measurement of kynurenine in the supernatant of IFN-γ-stimulated (1000 U/mL) 86HG39 glioblastoma cells cultured in IMDM medium with additional 100 µg/mL L-tryptophan for 72 h. During this stimulation period, the cells were treated with different 1-L-MT lots (grey bars) or 1-D-MT lots (shaded bars) (200 µg/mL each). (B) Kynurenine production within different 1-L-MT lots. 86HG39 cells were cultured in custom-made, tryptophan-free cell culture medium and stimulated with IFN-γ (1000 U/mL) for 72 h in the presence of 1-MT or L-trp (200 µg/mL). In both experimental groups the kynurenine content in the cell culture supernatants was determined by optical density at 492 nm +/− SEM, using Ehrlich's reagent. A significant inhibition of kynurenine production (A) and a significant increase in kynurenine production (B) (p<0.05) as compared to the negative control is marked with an asterisk (*) n = 3.