Background: Interleukin-6 (IL-6) and transforming growth factor-β (TGF-β) are implicated in the progression of IgA nephropathy, which is usually treated with corticosteroids.
Patients and methods: Urinary IL-6 and TGF-β were measured in 21 proteinuric patients with IgA nephropathy, before and after treatment with corticosteroids, to estimate the activity of the disease after remission of proteinuria.
Results: Urinary IL-6 and TGF-β levels at diagnosis were significantly higher in patients with IgA nephropathy compared to healthy subjects. TGF-β levels, were significantly higher in patients with proteinuria > 1 g/24 h and/or severe mesangial proliferation. Although a significant reduction of proteinuria was observed with corticosteroid treatment, urinary IL-6 and TGF-β levels remained elevated. Deterioration of renal function over a period of 5 years was observed in 3 patients. High urinary IL-6 levels at diagnosis represent a significant parameter distinguishing patients with progressive course in comparison to those with favorable clinical outcome (p = 0.01).
Conclusion: Treatment of patients with IgA nephropathy with corticosteroids is followed by remission of proteinuria but still increased urinary IL-6 and TGF-β excretion. This may be related to an ongoing inflammatory process within the kidney, and further research is required to estimate the value of urinary IL-6 and TGF-β as markers of activity of the disease.