Comparison of characteristics of natural autoantibodies against myeloperoxidase and anti-myeloperoxidase autoantibodies from patients with microscopic polyangiitis

Rheumatology (Oxford). 2011 Jul;50(7):1236-43. doi: 10.1093/rheumatology/ker085. Epub 2011 Mar 3.


Objective: Natural autoantibodies (NAAs) against MPO exist in normal human plasma. In the current study, the immune characteristics of MPO-NAA and MPO-ANCA were examined and compared with the aim to investigate the pathogenesis of MPO-ANCA.

Methods: MPO-NAAs were affinity purified from normal plasma of five healthy blood donors and one batch of IVIG. MPO-ANCAs were purified from plasma of 10 patients with MPA. Antigen specificity of the antibodies was tested by western blot analysis. The titre, the avidity, the Immunoglobulin G (IgG) subclasses and the effect of the antibodies towards the binding between ceruloplasmin and MPO were tested using ELISAs. The MPO-NAA-induced production of reactive oxygen species was assessed using oxidation of dihydrorhodamine (DHR) to rhodamine.

Results: MPO-NAA recognized epitope(s) in the heavy chains of MPO with conformation-dependent structure, the same as MPO-ANCA. The median titre of MPO-NAA was lower than that of MPO-ANCA (1 : 40 vs 1 : 4800, P < 0.001). The median avidity of MPO-NAA was lower than that of MPO-ANCA (2.2 × 10(7) vs 8.7 × 10(7)/M, P = 0.014). The IgG subclasses of MPO-NAA were mainly restricted to IgG1 (100%) and lack of IgG3. The inhibition effect on the binding between ceruloplasmin and MPO was lower for MPO-NAA than MPO-ANCA (P = 0.046). The MPO-NAA-induced respiratory burst of neutrophils was significantly weaker than that of MPO-ANCA (P = 0.036).

Conclusion: The lower titre, lower avidity and lack of IgG3 subclass compared with MPO-ANCA may contribute to the non-pathogenic co-existence of MPO-NAA with MPO in serum.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Antibodies, Antineutrophil Cytoplasmic / immunology*
  • Antibodies, Antineutrophil Cytoplasmic / metabolism
  • Autoantibodies / immunology
  • Autoantibodies / metabolism
  • Blotting, Western
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Humans
  • Immunoglobulin G / immunology*
  • Immunoglobulin G / metabolism
  • Male
  • Microscopic Polyangiitis / blood
  • Microscopic Polyangiitis / immunology*
  • Microscopic Polyangiitis / physiopathology
  • Neutrophils / immunology
  • Neutrophils / metabolism
  • Oxidation-Reduction
  • Peroxidase / metabolism*
  • Reference Values
  • Sampling Studies


  • Antibodies, Antineutrophil Cytoplasmic
  • Autoantibodies
  • Immunoglobulin G
  • Peroxidase