ABSTRACT
To detect serum interleukin -18 level and natural killer cell percentage in patients with systemic lupus erythematosus and to find out their correlation with disease activity and their role in lupus renal disease. The study included 30 female patients with systemic lupus erythematosus [15 patients with lupus nephritis and 15 patients without renal disease]. 10 apparently healthy females with matched age represent the control group. All patients were subjected to full history taking, thorough clinical examination, assessment of disease activity using modified systemic lupus erythematosus disease activity index [SLEDAI], laboratory investigations especially serum interleukin-18 level, natural killer [NK] cell percentage, serum urea, serum creatinine and 24 hours urinary protein. Serum level of interleukin-18 [IL-18] was significantly increased and percentage of NK cells was significantly decreased in patients with systemic lupus erythematosus [SLE] when compared to controls. In patients with SLE, increased serum IL-18 level showed significant negative correlation with NK cell percentage while this correlation was significantly positive with SLEDAI. Serum IL-18 level was significantly higher and NK cell percentage was significantly lower in SLE patients with lupus nephritis compared to those with no renal disease. In patients with lupus nephritis, increased serum IL-18 level showed significant positive correlation to serum urea, serum creatinine and 24 hours urinary protein, while reduced percentage of NK cells showed significant negative correlation with serum creatinine. The findings of this study may indicate that increased serum IL-18 levels and reduced NK cell percentage may play a role in pathogenesis and activation of SLE and renal involvement in this disease. Further studies are recommended for IL-18 as a potential target in treatment of autoimmune diseases including SLE