CD19 and systemic lupus erythematosus: BCMA receptor expression was decreased in the CD19+ B cells of SLE patients compared with those of HCs (median: 0.5% vs 13.10%, respectively; p < 0.01) (Fig. 1B) and in CD3+ cells (median: 36.00% vs 60.10%, respectively; p < 0.01) (Fig. 1C), while in plasma cells, the percentage of positive cells was increased in the SLE group (median of 69.85) compared with the HC group (median of 30.50; p < 0.01) (Fig. 1D).