Reduced numbers of CD39⁺ Treg cells in PBMCs of patients with MS. (A) Donor-specific variations in the number of the CD39⁺ Tregs. PBMCs of 2 healthy donors were stained for CD39 and CD4 expression. (B) Donor-specific ATP-hydrolysis capacity. CD4⁺CD25^high cells isolated from individuals containing either high numbers of CD39⁺ Tregs (approximately 40%; donor 1) or low numbers of CD39⁺ Tregs (< 3%; donor 2) were isolated and incubated with ATP as described in Figure 3B. (C) Fraction of CD25^high Treg cells in PBMCs of patients with MS. PBMCs of 74 healthy controls and 26 patients with MS were analyzed by FACS for the expression of CD4 and CD25. The relative fraction of CD4⁺CD25^high cells on total PBMCs is shown as a scatterplot. (D) Reduced numbers of CD39⁺ Treg cells in patients with MS. The cells shown in panel C were also analyzed for CD39 expression. The relative fraction on total PBMCs is shown for the CD4⁺CD25^highCD39⁻ (left panel) and the CD4⁺CD25^highCD39⁺ subsets (right panel). Asterisks indicate P < .001.