Urinary Excretion of Interleukin-6 in Pediatric IgA Nephropathy Patients

Abstract

Objective: Urinary excretion of interleukin-6 (U-IL6) has been reported to be elevated and to represent the disease activity in adult IgA nephropathy (IgAN). We investigated the significance and the utility of U-IL6 activity in pediatric IgAN patients. Methods: We evaluated 55 pediatric IgAN patients (4–18 years; mean age, 10.7 years) and 53 healthy controls from 2007 to 2012. The U-IL6 concentrations (pg/mg creatinine) were estimated by ELISA at the time of renal biopsy and after 6 months of prednisolone therapy for IgAN. In addition, we evaluated the correlations between the U-IL6 level and clinic pathological parameters of IgAN. To elucidate the usefulness for early diagnosis of IgAN, we investigated U-IL6 in 45 asymptomatic hematuria (ASH) children who were diagnosed by school urine screening program. Results: U-IL6 activity was significantly higher in IgAN patients than in healthy controls and ASH children (p<0.01). In addition, U-IL6 was significantly decreased after 6 months of prednisolone therapy (p<0.01). With regard to the clinicopathological parameters, U-IL6 activity was correlated with degree of proteinuria (p<0.01, r=0.72), hematuria (p<0.01, r=0.54), urinary podocyte score (p<0.01, r=0.59), mesangial cell proliferation (p<0.05), endocapillary proliferation (p<0.01), and crescent formation (p<0.05). Interestingly, five children who transited to IgAN from ASH during the observation period showed high U-IL6 levels (p<0.01). Conclusions: The present results also suggest that U-IL6 represents the disease activity in pediatric IgAN patients. We consider that it is important to evaluate U-IL6 in patients with ASH detected by school urinary screening program for early detection and prevention of unrecognized progression of IgAN.