Circulating levels of Tregs and B cells. (A) CD4⁺CD25^HighFoxp3⁺ Tregs were analyzed by FCM in controls (n = 26) and ITP patients (n = 20) at diagnosis. Dot plots of Treg levels are expressed as a percentage of CD4⁺ lymphocytes (left panel). Dot plots of circulating CD19⁺ B-cell levels observed in controls (n = 28) and ITP patients (n = 27) are expressed as a percentage of total circulating lymphocytes (right panel). The horizontal bars represent the mean values with standard deviations. (B) Circulating Treg levels expressed as a percentage of CD4⁺ lymphocytes were also measured before and after RTX in 8 patients (left panel). Circulating CD19⁺ B-cell levels assessed by FCM before and after RTX infusion (n = 13) are expressed as a percentage of total circulating lymphocytes (right panel). *P < .05; **P < .001; ***P < .0001; NS, nonsignificant.