CD19 and systemic lupus erythematosus: CD19+CD20+ B cells showed more prominent reductions in patients who received belimumab compared with patients who received ST alone from week 24 onward, with similar patterns observed for CD19+CD20+CD27– naïve B cells, CD19+CD20–CD27bright plasmablasts, and CD19+CD27brightCD38bright SLE-associated plasma cells from week 8 onward.