New therapeutic approaches of MS are emerging, targeting different actors of the immune system. Some of them target a specific population of white blood cells: B lymphocytes composed of different subpopulations. The subsets of B cells express different functional properties that control the immune response, but these regulation mechanisms have yet to be clearly described. Some subpopulations could amplify inflammation through IL-6 production for example, whereas some ones contribute to its regulation through the production of IL-10. Using samples collected in a large cohort of individuals with risk of MS and treatment-naive patients in the early onset of the disease, the investigators aim to develop a 2 year follow-up study of the different blood B cells subset distribution and their functional properties in terms of pro- and anti-inflammatory cytokine production in MS. This approach can identify new biomarkers for monitoring of MS patients and lead to better define the indication use of depletive B cell drugs and not to counteract the regulatory action of these cells.