Extended Data Fig. 1: Upregulation of Gch1 and BH4 in activated T cells.

a, Percentage of CD62L^lo GFP⁺ cells from purified Gch1-Gfp CD4⁺ T cells stimulated for 24 h with phorbol myristate acetate and ionomycin (50 ng ml⁻¹ each). Data are shown as means ± s.e.m., from n = 3 samples. The experiment was repeated two independent times. ***P < 0.001 (two-tailed Student’s t-test). b, c, Representative Gch1-Gfp expression in 16-h-activated (CD62L^low) CD4⁺ T cells after anti-CD3/CD28 stimulation (b) and representative dose–response of anti-(α)CD3/CD28 stimulation of purified CD4⁺ Gch1-Gfp T cells for 24 h (c). The experiment was repeated two independent times with similar results. d, Cell numbers of various immune populations in the thymus (left) and spleen (right) from control (n = 3) and Gch1;Lck (n = 3) 8-week-old mice. Data from individual mice are shown as means ± s.e.m. NS, not significant (two-tailed Student’s t-test). e, f, CD4⁺ (e) and CD8⁺ (f) T cell proliferation after three days of anti-CD3/28 stimulation, from control and Gch1;Lck mice. g, Representative histogram depicting the proliferation of DN3a thymocytes from control and Gch1;Lck mice cultured on OP9-Dl1 stromal cells for five days. The experiment was repeated two independent times with similar results. h, i, Representative FACS blot depicting the differentiation into CD4⁺ and CD8⁺ T cells of DN3a thymocytes from control and Gch1;Lck mice cultured on OP9-Dl1 stromal cells for five days (h), and quantification of the differentiated cell types from n = 3 animals (i). Data from individual mice are shown as means ± s.e.m. NS, not significant (two-tailed Student’s t-test).