P0419AUTOANTIGEN-SPECIFIC TH17 AND TH22 INFLAME THE KIDNEY IN ANCA-VASCULITIS

Abstract

Abstract Background and Aims Anti-neutrophil-cytoplasmic-antibody (ANCA)-associated-vasculitis (AAV) is an autoimmune small-vessel-vasculitis. T-cells play a pivotal role in pathogenesis as drivers of autoantibody formation and vasculitic damage. However, the involvement of T-cells in renal vasculitis is understood poorly. IL-17C is secreted by epithelial parenchymal cells enhancing the pathogenicity of Th17 cells. Furthermore, IL-17C is a chemotactic factor for Th17 cells. The aim of this study was to assess the role of Th17 cells and IL-17C in the pathogenesis of ANCA-vasculitis in an animal model of AAV. Method Wistar-Kyoto-rats were immunized with myeloperoxidase (MPO) in Freunds Adjuvant to induce AAV. Control rats were immunized with Freunds Adjuvant only. Albuminuria was determined weekly and rats were culled after two, four and six weeks. At the time of harvest, renal T-cells were isolated and characterized by flow cytometry. Antigen-specificity was determined by ELiSPOT. Petechial bleedings on the lung surface reflecting pulmonary vasculitis were quantified after harvest. Gene expression in spleen, kidneys and lungs was studied by PCR and is expressed as fold change over controls. IL-17C levels were measured in sera by ELISA. Results MPO-rats developed detectable titres of anti-MPO by week two. By week six, all MPO-animals developed renal vasculitis with significant albuminuria and pulmonary vasculitis. Accordingly, MPO animals showed significant crescent formation as compared to the controls (% of affected glomeruli: 11.4 ±10.5% vs. 0.4 ±0.7%, p<0.005). The petechial bleeding score on the lung surface was higher in MPO-immunized rats than in controls at week six (68 ±13 vs. 2 ±1, p<0.05). From week two on, Th17 and Th22 cells inflamed the kidney as determined by PCR and/or flow cytometry in MPO-rats. The Th17 and Th22 infiltrate was heaviest at week six post-immunization. The intra-renal T-cell response was skewed towards Th17 as compared to the frequency of splenic Th17 cells in MPO-rats (9.1 ±4.3% vs. 1.9 ±0.6%, p<0.005). The majority of intra-renal Th17 and Th22 cells was MPO-specific. Control rats did not show renal T-cell infiltration. Renal transcripts for IL-17C were slightly decreased in week 2 (0.88 ±0.1 fold), unchanged in week four (1.0 ±0.2) and slightly increased in week six after immunization (1.7 ±0.7 fold). Pulmonary IL-17C mRNA transcripts were decreased during weeks two and four after disease induction as compared to controls (0.29 ±0.07 fold, 0.98 ±0.2 fold). During week six, pulmonary IL-17C mRNA transcripts were slightly increased over controls (1.9 ±0.4 fold). Serum levels of IL17C were unchanged during weeks two to six after disease induction comparing MPO-immunized rats and controls. Conclusion Th17 and Th22 cells are drivers of renal inflammation in ANCA-vasculitis. The role of IL-17C in this cascade needs to be determined.