S100A8 and systemic lupus erythematosus: Indeed, both S100A8/A9 and S100A12 urine levels were significantly elevated in the urine of patients with SLE with active LN as compared with samples from patients with inactive or no renal disease, and calculated urine/serum ratios of both S100A8/A9 and S100A12 (from the same patients) were significantly elevated in patients with SLE with active LN.