Extended Data Fig. 9: T cells overproducing BH4 display enhanced ATP production, proliferation and autoimmunity.

a, Allergic airway inflammatory disease model and fold change of inflammatory cells in BALFs, comparing control and GOE;Lck mice. Data are shown as means ± s.e.m. n = 18 for control mice; n = 17 for GOE;Lck mice. *P < 0.05; **P < 0.01 (two-tailed Student’s t-test). b, Transfer colitis model. Changes in body weight of Rag2^−/− mice transferred with control (n = 6 animals) or GOE;Cd4 (n = 5) naive CD4⁺ T cells. Data are shown as means ± s.e.m. *P < 0.05; ***P < 0.001; NS, not significant (two-way ANOVA with Tukey’s multiple comparison test). c, Total numbers of activated (CD62L^lowCD44^high) CD4⁺ splenic T cells at three weeks post-transfer in mice transferred with control or GOE;Cd4 naive CD4⁺ T cells. Data for two mice from each group are shown. d, Transfer colitis model, involving transfer of naive CD4⁺ T cells (150,000 cells) and co-transfer of FACS-purified T-reg cells from control (n = 5) and GOE;Cd4 (n = 6) mice. Changes to initial body weights were scored over seven weeks. Data are shown as means ± s.e.m. ***P < 0.001; NS, not significant (two-way ANOVA with Tukey’s multiple comparison test). e, Representative histograms depicting the proliferation of purified unstimulated and anti-CD3/28-stimulated CD4⁺ and CD8⁺ wild-type and Gch1;RORc T cells treated for three days with sepiapterin (5 μM). The profile for the unstimulated T cells of each genotype is shown in grey. Experiments were repeated three independent times with comparable results. f, g, Representative FACS plots showing EdU-based cell-cycle analysis following 28-h anti-CD3/28 stimulation of control CD4⁺ T cells, GOE;Cd4 CD4⁺ T cells, control CD4⁺ T cells treated with sepiapterin (5 μM), and GCH1;RORc CD4⁺ T cells treated with sepiapterin (5 μM) (f); and quantification of the S-phase-entry population (g). EdU was pulsed for the last 4 h of stimulation. n = 4 mice for control; n = 3 mice for all other genotypes. ***P < 0.001 (one-way ANOVA with Dunnett’s multiple comparisons test). h, i, Effect of BH4 on the proliferation (³H-thymidine incorporation; h) and IL-2 secretion (i) of CD4⁺ wild-type T cells activated with anti-CD3/28 antibodies for 24 h and treated with vehicle (n = 3/4) or BH4 (10 μM; n = 3/4). Data are shown for individual mice as means ± s.e.m. **P < 0.01 (two-tailed Student’s t-test). j, Representative histograms depicting the proliferation of control and Gch1;RORc CD4⁺ T cells after three days of anti-CD3/28 stimulation supplemented with BH4 (10 μM). FACS blots are representative of two independent experiments with comparable results.