Serum levels of interleukin-12, interleukin-15 and interleukin-18 and their association with disease activity in patients with systemic lupus erythematosus

Abstract


Systemic lupus erythematosus (SLE) is a highly heterogenous disorder in which multiple immunologic abnormalities have been described. In this study we investigate the serum concentration of interleukin (IL)-12, IL-15 and IL-18 using an enzyme-linked immunosorbent assay (ELISA) in 60 patients with SLE and 20 healthy controls. We also examined a possible association between the serum levels of those proteins and SLE activity as well as particular clinical and laboratory parameters and immunosuppressive treatment. The levels of all three interleukins was higher in SLE patients than in normal persons. There was also a positive correlation between IL-12, IL-15 and IL-18 serum concentration and SLE activity score, but associations were not statistically significant (p>0.05). We found a significant positive correlation between IL-12 and IL-18 ((=0.419, p<0.001) and IL-15 and IL-18 ((=0.500; p<0.001). The level of IL-18 was higher in the SLE patients with serum antinuclear antibodies (median 660.0 pg/ml) than in patients without antinuclear antibodies (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 the patients with skin immunoglobulin deposits (328.9 pg/ml) than without this phenomenon (257.0 pg/ml) (p<0.05). The levels of all three cytokines in the patients treated and untreated with immunosuppressive drugs were similar.
In conclusion, serum levels of IL-12, IL-15 and IL-18 are higher in SLE patients than in healthy controls. These cytokines may play a role in SLE pathogenesis. Monoclonal antibodies or factors neutralising these cytokines may be of value in SLE treatment.