CD19 and systemic lupus erythematosus: Further study showed that the percentage of circulating CD19+IL-10+ B cells was expanded in patients with active SLE (3.44±0.69%, n = 6) than that of healthy controls (1.15±0.45%, n = 6, Figure 3C), while the absolute numbers of CD19+IL-10+ B cells were not significantly different between SLE patients and healthy controls (Figure S3B).