Iwatta et al. previously reported that CD19+/CD24hi/CD38hi/CD27+/IL-10+ B10-cell frequencies in blood from a group of patients with autoimmune diseases, such as lupus, rheumatoid arthritis, SS, autoimmune skin disease, and multiple sclerosis, were not significantly different from those observed in healthy controls, although mean B10 and B10 pro-cell frequencies were significantly increased. Here, CD27 is linked to rheumatoid arthritis.