Fig. 3.

Dose-dependent regulatory T cell (T_reg)-mediated suppression of effector T cells (T_eff). Proliferation was assessed by [³H]-thymidine incorporation. Percentage of suppression of proliferation in co-cultures of T_regs and T_effs was calculated by dividing the mean counts per minute (cpm) of co-culture wells by the mean cpm obtained from T_effs cultured alone. (a) Left panel illustrates the gate discriminating CD4⁺ cells and the right panel shows the gates for sorting CD25^hiCD127^lo (T_regs) and CD25^–CD127^+/hi cells (T_effs). (b) Suppression exerted by T_regs from patients treated with placebo (n = 3, square) and glutamic acid decarboxylase (GAD)-alum (n = 4, circle) is shown as median for each group. (c) Suppression exerted by T_regs from type 1 diabetes (T1D) patients on autologous T_effs (red downward triangle; n = 7), by healthy T_regs on autologous T_effs (green circle), by T1D T_regs in co-culture with healthy T_effs (blue square) and by healthy T_regs in co-culture with T1D T_effs (purple upward triangle). The suppression is shown as percentage of decrease in T_eff proliferation in the presence of T_regs compared to T_effs cultured in the absence of T_regs. Healthy represents repeated measurements (n = 7) of one healthy reference. (d) Left panel illustrates suppression exerted by healthy T_regs in cross-culture with patient T_effs and the right panel shows suppression exerted by patient T_regs in cross-culture with healthy T_effs. Statistical significances are shown as P-values: *P < 0·05; **P < 0·01; ***P < 0·001. Data points indicate medians, error bars designate interquartile range.