Original study
For inclusion in the study, we selected patients with newly diagnosed or
relapsing AAV, who had a Birmingham Vasculitis Activity Score version 3
(BVAS v. 3) of ≥3. Diagnosis of granulomatosis with polyangiitis (GPA)
or microscopic polyangiitis (MPA) was established according to the
American College of Rheumatology criteria [11], EMA algorithm
[12] and the Chapel Hill Conference Consensus definition [13].
Healthy control subjects were recruited at Tareev Clinic of Internal
Disease (Moscow) and Vladimir Regional Clinical Hospital. All subjects
provided written informed consent approved by the local ethics committee
of the Sechenov University. The study was in compliance with the
Declaration of Helsinki Principles.
Plasma concentrations of human complement components were determined by
enzyme-linked immunosorbent assay, including MAC (HK328-02, Hycult
Biotech, the Netherlands), C5a (HK349-01, Hycult Biotech, the
Netherlands), C3a (HK354-01, Hycult Biotech, the Netherlands), factor B
(EF7001-1, ASSAYPRO, USA), and properdin (factor P; SEA783Hu,
Cloud-Clone Corporation, USA). All the complement components were
assayed according to the manufacturer’s instructions. Upper reference
limits (the 97.5th percentile) for each complement
component were defined from the values in the control group after log
transformation of the primary data.
Renal biopsies were evaluated according to a standardized protocol
[14]. ANCA-associated glomerulonephritis class was established
according to the Berden classification [15]. The percentage of
glomeruli with crescents and global sclerosis was calculated as the
percentage of the total number of glomeruli in a biopsy. Interstitial
fibrosis and tubular atrophy are given as the percentage of the
tubulointerstitial compartment affected. Deposition of IgA, IgG, IgM,
C3, kappa and lambda light chains was scored semi-quantitatively by
immunofluorescence staining.