Abstract
Objective To investigate expression of terminal complement components C3a and C5a on circulating myeloperoxidase (MPO)-positive microparticles (MPO+MPs) in relation to disease activity and renal involvement in patients with 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+MPs expressing C3a and C5a was analysed 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+MPs compared to controls (p<0.0001, respectively). When the group of patients with active AAV was divided according to the presence of renal activity, the concentration of MPO+MPs expressing C3a and C5a was significantly higher in patients with renal involvement compared to patients with non-renal disease and controls (p<0.05, 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 non-renal groups. There was significant correlation between the disease activity measured by BVAS and the levels C3a and C5a expressed on MPO+MPs.
Conclusion Determination of C3a and C5a on MPO+MPs might be considered as a potential novel biomarker of renal involvement in patients with AAVs and may be of importance in the pathogenetic process.