TY - JOUR T1 - Microparticles Expressing Myeloperoxidase and Complement C3a and C5a as Markers of Renal Involvement in Antineutrophil Cytoplasmic Antibody–associated Vasculitis JF - The Journal of Rheumatology JO - J Rheumatol DO - 10.3899/jrheum.181347 SP - jrheum.181347 AU - Aleksandra Antovic AU - Fariborz Mobarrez AU - Milena Manojlovic AU - Nida Soutari AU - Victoria De Porta Baggemar AU - Annica Nordin AU - Annette Bruchfeld AU - Jelena Vojinovic AU - Iva Gunnarsson Y1 - 2019/08/01 UR - http://www.jrheum.org/content/early/2020/01/10/jrheum.181347.abstract N2 - Objective To investigate expression of terminal complement components C3a and C5a on circulating myeloperoxidase (MPO)-positive microparticles (MPO+MP) in relation to disease activity and renal involvement in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods Forty-six clinically well-characterized patients with AAV and 23 age- and sex-matched healthy controls were included. The concentration of MPO+MP expressing C3a and C5a was analyzed from citrate plasma by flow cytometry. Serum levels of C3a and C5a were determined using commercial ELISA. The assessment of vasculitis disease activity was performed using the Birmingham Vasculitis Activity Score (BVAS). Among patients, 23 had active disease with BVAS ≥ 2 and 14 patients had active renal flares. Results AAV patients had significantly increased expression of C3a and C5a on MPO+MP compared to controls (both p < 0.0001). When the group of patients with active AAV was divided according to the presence of renal activity, the concentration of MPO+MP expressing C3a and C5a was significantly higher in patients with renal involvement compared to patients with nonrenal disease and controls (p < 0.05 and p < 0.01, respectively). The serum levels of C3a were significantly decreased (p < 0.01) in the renal subgroup, while there were no changes in serum levels of C5a comparing the renal and nonrenal groups. There was significant correlation between the disease activity measured by BVAS and the levels of C3a and C5a expressed on MPO+MP. Conclusion Determination of C3a and C5a on MPO+MP might be considered as a novel biomarker of renal involvement in patients with AAV and may be of importance in the pathogenetic process. ER -