As shown in Table 2, after treatment with belimumab CD19+ B lymphocytes decreased in patients with SLE, both in percentages (T0 vs. T6: p = 0.02; T6 vs. T12: p = 0.02; T0 vs. T12: p = 0.002) and absolute numbers (T0 vs. T6: p = 0.009; T0 vs. T12: p = 0.005). This evidence concerns the gene CD19 and systemic lupus erythematosus.