Reduction in IL-10 producing B cells (Breg) in multiple sclerosis is accompanied by a reduced naïve/memory Breg ratio during a relapse but not in remission.

In this study, we assessed B cell subsets, including Bregs, during stable and active disease in relapsing remitting multiple sclerosis (RRMS) patients and related B cell subsets to vitamin D status. We report that RRMS patients have a decreased percentage of both memory B cells and Bregs compared to healthy controls. During a relapse, the reduction in Bregs involved in particular naïve Bregs. We found no correlation between vitamin D status and B cell subsets. An effect of vitamin D on Bregs cannot be ruled out, since it might be the function that is interfered with instead of relative numbers.