Proinflammatory interferon-γ-inducing monokines (interleukin-12, interleukin-18, interieukin-15) -: serum profile in patients with systemic lupus erythematosus

Concentrations of three interferon-gamma- inducing monokines, IL-12, IL-18 and IL-15, were investigated in the serum of 60 patients with systemic lupus erythematosus (SLE) and 20 healthy subjects. IL-12 and IL-18 were detectable in the serum of all patients with SLE and in all healthy controls. The level of IL-12 was significantly higher in SLE patients (median 264.9 pg/ml) than in the control group (median 163.6 pg/ml, p < 0.02). Similar differences were observed in the level of IL-18 (median values 602.2 pg/ml and 252.7 pg/ml, respectively, p < 0.001). Correlations between serum levels of IL-12 and IL-18 and SLE activity were not statistically significant (p > 0.05). We found a significant, positive correlation between IL-12 and IL-18 (rho = 0.419, p < 0.001) in SLE patients. The level of IL-18 was higher in the SLE patients with antinuclear antibodies (ANA) (median 660.0 pg/ml) than in ANA-negative patients (median 326.5 pg/ml, p < 0.03), as well as in patients with immunoglobulin deposits at the dermal-epidermal junction (median 746.0 pg/ml and 444.0 pg/ml respectively, p < 0.04). The level of IL-12 was also higher in patients with skin immunoglobulin deposits (328.9 pg/ml) than those without this phenomenon (257.0 pg/ml, p < 0.05). The levels of both cytokines in the patients treated with immunosuppressive drugs and those patients not treated were similar. The serum levels of IL-15 were low and not significant both in SLE patients (median 2.9 pg/ml), and in healthy controls (median 1.6 pg/ml). In conclusion, serum levels of IL-12 and IL-18 are higher in SLE patients than in healthy controls which may indicate a role in the disease pathogenesis. However, they do not correlate with disease activity and seem to be unresponsive to immunosuppressive treatment.