A reduction in the percentage of BR3+ B cells in parallel with the decreased BR3 MFI in SLE patients and HVs is consistent with the results of Shabgah et al., which showed a decreased percentage of CD19+ BR3+ and CD19+ BCMA+ B cells 12 months after MSC transplantation in patients with rheumatoid arthritis [41]. Here, CD19 is linked to rheumatoid arthritis.