CD19 and systemic lupus erythematosus: After treatment with Belimumab, B lymphocytes decreased in patients with SLE, both in percentages (T0, T6 and T12 = 8.1, 3.8 and 3.1 % of CD19 on total lymphocytes) and absolute numbers (T0, T6 and T12 = 82.3, 17.3 and 21.1 cell/μl).