B1 cells are unaffected by immune modulatory treatment in remitting–relapsing multiple sclerosis patients

• B1 cells are diminished in RRMS patients.
• Immune modulatory treatment does not affect the frequency of B1 cells.
• Immune modulatory treatment has no effect on CD11b+ B1 cells.
• B1 cells might not contribute to the plasmablast pool.

In this study we aimed to investigate whether treatment with an immune modulatory drug had an effect on the distribution of B cell subpopulations in patients with remitting–relapsing multiple sclerosis (RRMS). We investigated the first-line drugs glatiramer acetate, interferon-β and natalizumab. Our data show that the frequency of the CD27+CD43+ B1 cell subset was significantly diminished in RRMS patients compared to healthy subjects and that this subset was unaffected by treatment. Regardless of their true nature, we believe that these cells are part of the autoimmune disease pattern.