Suppressed pro-inflammatory properties of circulating B cells in patients with multiple sclerosis treated with fingolimod, based on altered proportions of B-cell subpopulations

•Fingolimod reduce circulating B cells in patients with MS.•The remaining B cells produce less TNFα, more IL-10, and express less CD80.•Fingolimod reduce proportion of memory and increase that of transitional B cells.•The suppressed B-cell activities are related with the effect of fingolimod in MS.

The chief therapeutic mechanism of fingolimod in multiple sclerosis (MS) is considered to be sequestration of pathogenic lymphocytes into secondary lymphoid tissues. B cells have recently been recognized as important immune regulators in MS. In this study, the effects of fingolimod on B cells in MS patients were analyzed. MS patients treated with fingolimod (MS-F) had a significantly lower number of B cells in the circulation. The remaining B cells in the blood of MS-F had a reduced proportion of memory B cells and an increased proportion of naïve B cells, expressed lower levels of the costimulatory molecule CD80, and produced less tumor necrosis factor-α and more interleukin-10. These observations in MS-F were based on an increased proportion of the transitional B-cell subpopulation within the naïve B-cell compartment. The observed findings in B cells of MS-F might be related to the therapeutic effect of this drug in MS.