[Inhibition of oxidative activity of myeloperoxidase by anti-myeloperoxidase antibodies from patients with microscopic polyangiitis].
OBJECTIVE
To investigate the inhibitory effects on myeloperoxidase (MPO) oxidation activity by affinity-purified anti-MPO antibodies from patients with microscopic polyangiitis (MPA) and to further investigate the interaction between MPO, ceruloplasmin and anti-MPO antibodies.


METHODS
Human IgG fractions were purified from plasma of 11 patients with anti-MPO antibody positive MPA and sera of 12 normal controls. Anti-MPO antibodies were further purified from anti-MPO antibody containing IgG fractions using MPO affinity chromatography. The enzyme activity of MPO was measured, in the presence of anti-MPO antibodies and normal IgG preparations, using a classical MPO oxidation assay. Interaction between ceruloplasmin, MPO and anti-MPO antibodies was further investigated using ELISA.


RESULTS
Anti-MPO antibodies from 7/11 patients with MPA could inhibit the MPO activity as non-competitive inhibitors in a dose-dependent manner. Ceruloplasmin could competitively inhibit the oxidation activity of MPO in a dose-dependent and time-dependent manner. Anti-MPO antibodies could inhibit the binding between MPO and ceruloplasmin to a maximum of (75.4+/-11.6)%.


CONCLUSIONS
Anti-MPO antibodies, from the majority of patients with MPA, could inhibit the oxidation activity of MPO and interfere with the binding between MPO and ceruloplasmin.
Chen
Jie
J
Renal Division, Peking University First Hospital, Beijing 100034, China.
Chen
Min
M
Liu
Zhang suo
Zs
Zhao
Ming hui
Mh
D000328:Adult; D000368:Aged; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D002570:Ceruloplasmin / Q000378:metabolism; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D055953:Microscopic Polyangiitis / Q000201:enzymology* / Q000276:immunology*; D008875:Middle Aged; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D009195:Peroxidase / Q000276:immunology* / Q000378:metabolism*
D019268:Antibodies, Antineutrophil Cytoplasmic; D007074:Immunoglobulin G; D009195:Peroxidase; D002570:Ceruloplasmin