Compositional Changes of B and T Cell Subtypes during Fingolimod Treatment in Multiple Sclerosis Patients: A 12-Month Follow-Up Study

Background and objective: The long term effects of fingolimod, an oral treatment for relapsing-remitting (RR) multiple sclerosis (MS), on blood circulating B and T cell subtypes in MS patients are not completely understood. This study describes for the first time the longitudinal effects of fingolimod treatment on B and T cell subtypes. Furthermore, expression of surface molecules involved in antigen presentation and costimulation during fingolimod treatment are assessed in MS patients in a 12 month follow-up study. Methods: Using flow cytometry, B and T cell subtypes, and their expression of antigen presentation, costimulation and migration markers were measured during a 12 month follow-up in the peripheral blood of MS patients. Data of fingolimod-treated MS patients (n = 49) were compared to those from treatment-naive (n = 47) and interferon-treated (n = 27) MS patients. Results: In the B cell population, we observed a decrease in the proportion of non class-switched and class-switched memory B cells (p,0.001), both implicated in MS pathogenesis, while the proportion of naive B cells was increased during fingolimod treatment in the peripheral blood (PB) of MS patients (p,0.05). The remaining T cell population, in contrast, showed elevated proportions of memory conventional and regulatory T cells (p,0.01) and declined proportions of naive conventional and regulatory cells (p,0.05). These naive T cell subtypes are main drivers of MS pathogenesis. B cel