The percentages of mature B cells (CD19+IgD+) was higher in RA patients (3.02±0.26) than healthy controls (2.20±0.26) (P = 0.033) (Fig 1B–1D), while that of immature B cells (CD19+IgM+IgD-) was lower in RA patients than healthy controls (0.48±0.10 vs. 1.53±0.20, P < 0.001[S1 Fig]). The gene discussed is CD19; the disease is rheumatoid arthritis.