SERUM AND URINARY INTERLEUKIN-6 IN SYSTEMIC LUPUS-ERYTHEMATOSUS

Dysregulation of IL-6 production has been proposed as a pathogenic mec hanism in SLE. We asked if serum or urine IL-6 levels could serve as i ndicators of systemic lupus erythematosus (SLE) disease activity. Usin g a sensitive enzyme-linked immunosorbent assay (ELISA), we measured s erum and urine IL-6 in 56 SLE patients. Disease activity was assessed using a standard clinical index, the Systemic Lupus Activity Measure ( SLAM). Only seven of 56 SLE patients had elevated serum IL-6 levels, c ompared with 1 of 32 controls (NS). SLE disease activity did not corre late with serum IL-6 levels. Sixteen of 50 SLE patients in whom urine IL-6 was measured exhibited elevated urine IL-6 levels, compared with 1 of 17 controls (p = < 0.05). Urine IL-6 levels correlated with overa ll disease activity and with the presence of active urinary sediment. Our results indicate that serum IL-6 is not a predictor of disease act ivity in SLE, but that urine IL-6 may be a marker of active nephritis.