Background: Immunoglobulin A vasculitis (IgA-V), formerly known as Henoch-Schönlein purpura (HSP), is the most common small vessel vasculitis in children. In recent years, the role of T cells in the pathogenesis of HSP/IgA-V has become a focus of research.
Methods: Renal biopsy specimens from 22 pediatric patients diagnosed with Henoch-Schönlein nephritis (patient group) were compared to normal renal tissue in nephrectomy specimens from 20 pediatric patients diagnosed with Wilms tumor (control group). All renal specimens were scored according to International Study of Kidney Disease in Children (ISKDC) and Oxford classification. Immunohistochemical analyses of interferon-gamma (IFN-γ), interleukin (IL)-4, IL-17 and FOXP3 expression were performed.
Results: All glomeruli and tubules of the HSP/IgA-V patients showed significantly higher IFN-γ and IL-17 expression than those of the control group. Glomerular IFN-γ and IL-17 staining grades correlated with the urinary protein/creatinine ratio (r = 0.62, p = 0.02 and r = 0.507, p = 0.016, respectively). IL-17 expression also correlated with the percentage of crescents (r = 0.518, p = 0.014). IL-4 staining was present in only nine of the 22 patient biopsies and did not correlate with any of the parameters studied. Interstitial areas of patient biopsies had more FOXP3+ cells/μm(2) than those of the control group (p < 0.001), but differences in glomerular and tubular FOXP3+ levels (cells/μm(2)) between the two groups were not statistically different. The ISKDC and Oxford scores did not correlate with any parameter studied. However, endocapillary hypercellularity did correlate with IFN-γ expression.
Conclusions: Based on these results, we conclude that IFN-γ and IL-17 contribute to HSP/IgA-V in children.