Comparison of PD-1 expression in clinical responders and nonresponders during low-dose IL-2 therapy. (A) Scatter plot of the percentage of PD-1⁺CD45RA^– Tregs and Tcons in nonresponders and responders at week 2 during IL-2 therapy. (B) Ratio of Treg percentage of PD-1⁺:Tcon percentage of PD-1 in nonresponders and responders before and 2 weeks after starting IL-2 therapy. The ratio is significantly increased in clinical responders 2 weeks after IL-2 administration (P = .03, Wilcoxon signed rank test). Median values are shown in green.