A high CD27⁺T_REG/CD27^-T_REG ratio corresponds to potent suppression. The relative suppression (y axis) at a suppressor-to-effector ratio of 1:128 was plotted against the corresponding CD27⁺T_REG/CD27^-T_REG subset ratio (x axis) for the ^ExpT_REG pool (♦), the ^ExpT_REG CsA pool (cultured with 400 ng/mL CsA) (▪), and the ^ExpT_REG rapamycin pool (cultured with 100 nM rapamycin) (▴). The results of 6 independent experiments are shown.