Plasma IL-2 levels and fold change in absolute CD4Treg numbers during IL-2 therapy. (A) Pediatric cohort. (B) Adult cohort. Blue lines denote plasma IL-2 concentrations (pg/mL), red lines denote fold change (FC) in absolute CD4Treg count from baseline (W0). Median values (circles) and the IQR (whisker bars) are shown at each time point. The number of patients evaluated at each time point is indicated below.