Elevation of proinflammatory cytokine (IL-18, IL-17, IL-12) and Th2 cytokine (IL-4) concentrations in patients with systemic lupus erythematosus

Previous studies have indicated that the autoimmune phenomenon might be caused by an imbalance of T helper cell (Th) cytokines. We measured the plasma concentrations of three novel proinflammatory cytokines interleukin (IL)-17, IL-18, IL-12 and a key Th2 cytokine IL-4 in patients with systemic lupus erythematosus (SLE) and correlated the ratio of proinflammatory/Th2 cytokines with SLE disease activity index (SLEDAI). Plasma IL-12, IL-17, IL-18 and IL-4 concentrations of 36 SLE patients and 18 sex- and age-matched control subjects were measured by enzyme linked immunosorbent assay. All were significantly higher in SLE patients than control subjects (IL-12, mean +/- s.d. of 166.7 +/- 84.5 vs 93.5 +/- 39.2 pg/ml, P < 0.001; IL-17, 76.5 +/- 45.7 vs 37.6 +/- 35.3 pg/ml, P = 0.002; IL-18, 368.7 +/- 199.5 vs 141.1 +/- 47.1 pg/ml, P < 0.001; and IL-4, 27.1 +/- 15.3 vs 17.3 +/- 7.2 pg/ml, P < 0.05), and IL-18/IL-4 ratio correlated positively and significantly with SLEDAI score (r = 0.435, P = 0.006). We propose that SLE is characterized by an elevation of both Th1 and Th2 cytokines: the elevation of proinflammatory cytokine IL-12, IL-17 and IL-18 may trigger the inflammatory process in SLE and elevation of IL-18/IL-4 ratio suggests an imbalance of cytokine profile to mediate the inflammatory response.