CD19 and rheumatoid arthritis: In detail, post-switch memory B cells (p = 0.013, mean ± SEM in RA = 7.8 ± 0.6% vs. HD = 4.9 ± 0.7%); pre-switch memory (CD19+IgD+CD27+Ki-67+) B cells (p = 0.0002, RA = 5.3 ± 0.5% vs. HD = 2.2 ± 0.3%); DN memory B (CD19+IgD-CD27-Ki-67+) cells (p = 0.010, RA = 3.8 ± 0.3% vs. HD = 2.5 ± 0.3%), and in naïve B (CD19+IgD+CD27-Ki-67+) cells (p = 0.89, RA = 0.6 ± 0.1% vs. HD = 0.6 ± 0.1%).