ABSTRACT
lnterleukin-18 [IL-18] and its inducer IL-12 have multiple biological activities that are important in generating Th1 responses and inflammatory tissue damage. We investigated serum concentration of the novel pro-inflammatory Th1 cytokine; IL-18, and its inducer IL-12 in patients with immune rheumatic diseases. Group I comprised 32 patients of systemic lupus erythmatosus [SLE], Group II comprised 36 patients of rheumatoid arthritis [RA]. Group III comprised 9 patients [2 patients of Behcet, 2 patients of Dermatomyositis, 2 patients of Sicca syndrome, one patient of Scleroderma, and 2 patients of Mixed connective tissue disease]. Group IV is a control group consists of 21 sex and age matched healthy subjects and correlated their levels with autoantibody concentration [ANA and ds-DNA], clinical grades and SLE disease activity index [SLEDAI]. Serum IL-18, IL-12 ,ANA and ds-DNA were measured by enzyme immune sorbent assay. IL-18, IL-12 and ANA were significantly higher in the three studied groups than in the control group [IL-18; P<0.001 in the three groups, IL-12; P=0.019, P=0.002, and P= 0.006, and ANA; PO.001, P=0.002,and P=0.006, respectively].ds-DNA was significantly higher in SLE patients than in control group [P<0.001].There were significant positive correlations between; A] levels of IL-18,and both ANA and ds-DNA in SLE patient [r=0.41,P=0.001, r= 0.58 and P=0.001 respectively]; and B] IL-18 and ANA in both RA and group III patients [r= 0.32, P=0.005,r=0.61 and P= 0.022 respectively]. Also, there were significant positive correlation between the levels of IL-18 and clinical grades of the three groups [r=0.60, P=0.001, r=0.79, P=0.001, r=0.78 and P= 0.001 respectively]. In SLE patients ,IL-18 concentration shows significant positive correlation with SLEDAI score [r= 0.76 ,P=0.001]. In conclusion, the elevation of proinflammatory cytokines [IL-18 and IL-12] may trigger the inflammatory process in immune rheumatic diseases and IL-18 is correlated with disease activity