Fig. 1.

T cells regulate kynurenine transport through a System L transporter. a Uptake of ³H-kynurenine (0.1 μCi/ml, 4 min, 37 °C) in purified CD4⁺ T cells ± TCR activation using CD3/CD28 antibodies for 18 h; in vitro expanded TH1 cells (5 days) and in vitro expanded CTLs (5 days). Cold competition with non-radiolabelled kynurenine is shown as a control for uptake specificity. b Uptake of ³H-kynurenine (0.1 μCi/ml, 4 min, 37 °C) or ³H-glutamine (0.5 μCi/ml, 4 min, 37 °C) performed in Na⁺ containing or Na⁺-free uptake buffer. The graphs show radiolabelled tracer uptake in purified CD4⁺ T cells 48 h post TCR activation using CD3/CD28 antibodies (left panel); IL-2 maintained TH1 cells (centre panel) and IL-2 maintained CTLs (right panel). c–e Radiolabelled tracer uptake in IL-2 maintained TH1 cells (top panels) and IL-2 maintained CTLs (bottom panels) in the presence of non-radiolabelled substrate (5 mM; cold competition) or the System L inhibitor, BCH (5 mM). The graphs show ³H-tryptophan (c), ³H-kynurenine (d) and ³H-glutamine (e). Error bars are ±s.d. Individual points represent biological replicates. a–e Three biological replicates. P values * = < 0.01; ** = < 0.005; *** = < 0.001; **** = < 0.0001; ns = not significant (ordinary one-way ANOVA)