To our surprise, c-Myc expression strongly enhanced the production of kynurenine in all IFN-γ-treated samples whereas infection alone or in cells with constant c-Myc expression had no effect (Figure 5I), suggesting that the relatively low Trp levels in the IFN-γ-treated, c-Myc-expressing cells depend on an increased turn-over. This evidence concerns the gene IFNG and infection.