Th17 expansion in MS patients is counterbalanced by an expanded CD39 ⁺ regulatory T cell population during remission but not during relapse

In this study, percentages of CD39 ⁺ Treg and Th17 cells were compared between relapsing-remitting MS patients and controls and were related to the vitamin D status. The Th17 cell population was expanded in about 40% of the MS patients. In MS patients in remission, but not during relapse, a positive association was found between Th17 cell and CD39 ⁺ Treg percentages (r=0.468, p=0.007). Since CD39 ⁺ Tregs have been shown to have Th17 suppressive capacities, we propose that a dysregulated Th17/CD39 ⁺ Treg balance might contribute to disease exacerbation. A clear role for vitamin D in this regulation could not be established.