CD19 and systemic lupus erythematosus: No difference was observed between flaring and non-flaring patients regarding rapid or early changes in CD19+CD20+ B cells (P=0.630 and P=0.082, respectively), CD19+CD20+CD69+ activated B cells (P=0.439 and P=0.681, respectively), CD19+CD20-CD27bright plasmablasts (P=0.967 and P=0.772, respectively), or CD19+CD27brightCD38bright SLE-associated plasma cells (P=0.681 and P=0.366, respectively).