Interleukin-18 in urine and serum of children with idiopathic nephrotic syndrome

Abstract

Background/aims: Interleukin (IL)-18, a member of the IL-1 cytokine superfamily, is recognized as an important regulator of immune responses. The aim of our study was to investigate the IL-18 levels in serum and urine from children with idiopathic nephrotic syndrome (INS) during relapse and remission, and to evaluate the role of IL-18 in this disease.

Methods: 67 children with INS, aged 3-16 years, and 15 normal controls were included in the study. The patients were divided into two groups according to activity of the disease: I (n = 37) - INS in relapse, II (n = 30) - INS in remission. Serum and urinary IL-18 were determined by ELISA and in urine related to the urinary creatinine (Cr) concentration. Serum creatinine, protein, albumin and 24-hour proteinuria were measured in children with INS.

Results: Urinary IL-18 concentration was significantly higher in group I (213.51 +/- 162.15 pg/mg Cr) compared to group II (64.74 +/- 10.95 pg/mg Cr) and to normal controls (37.03 +/- 4.1 pg/mg Cr, p < 0.001). Serum IL-18 concentration was significantly higher in group I than in the controls (146.4 +/- 30.2 and 113 +/- 10 pg/ml, respectively; p < 0.05); the differences between either groups I and II or group II and controls were not significant. Urinary IL-18 correlated positively with serum IL-18 and with urinary protein excretion, but no correlations were found with other laboratory data.

Conclusion: Increased serum and urine IL-18 levels were observed during relapse of INS. These findings indicate the association between the active phase of INS and the levels of IL-18 and can suggest the role of this cytokine in the INS development. The changes in urinary IL-18 excretion in the course of INS are connected with the disease activity.