Surface expression of immunoglobulin isotypes during IL-6R inhibition. (A) Representative FACS plots showing the expression of immunoglobulin isotypes, IgA, IgG and IgM on gated DN and post-switch B cells. (B) During IL-6R inhibition, IgA+ DN B cells decreased significantly from 24.7 (10.0 to 64.2) percent median (range) to 18.4 (4.8 to 34.7) at week 12 (P = 0.004) and 20.5 (4.6 to 33.8) at week 24 (P = 0.04) respectively. There were no remarkable changes in relative IgG+ and IgM+ DN B Cells. (C) IgA+ and IgG+ post-switch B cells were not influenced during IL-6R inhibition. BL, baseline, W12, week 12 and W24, week 24. DN, double-negative; Ig, immunoglobulin; IL-6R, interleukin-6 receptor.