CD19 and systemic lupus erythematosus: Successful B cell depletion therapies in autoimmune diseases such as anti-CD20 mAb treatment of patients with rheumatoid arthritis (RA) or multiple sclerosis (MS) and anti-CD19 CAR T cell treatment of patients with systemic lupus erythematosus (SLE) revealed the essential role for B cells in human autoimmune syndromes (6–8).