[The relationship between subclassification of anti-myeloperoxidase IgG by enzyme-linked immuno-sorbent assay analysis and vasculitis activity].

OBJECTIVE

Antineutrophil cytoplasmic antibody (ANCA) is an important serological diagnostic tool for certain vasculitides, such as Wegener's granulomatosis and microscopic polyangiitis. Several studies suggested that ANCA titers correlated with disease activity. However, in some patients, ANCA still remained positive when patients were in clinical remission. The major isotype of ANCA is IgG, which has four subclasses. This study is to investigate the relationship between anti-MPO IgG subclasses and vasculitis activity.

METHODS

Serum samples, taken from 30 anti-myeloperoxidase (MPO) antibody positive patients both in active phase and in remission, were analysed by ELISA for their anti-MPO IgG subclass distribution and the change of anti-MPO IgG subclasses was compared with the change of anti-MPO IgG antibodies.

RESULTS

All four anti-MPO IgG subclasses were positive in active phase, IgG(4) being the highest. In remission, the level of anti-MPO IgG(1) and IgG(3) subclasses decreased the most and the percentage of negative change of IgG(3) was the highest, even more significant than that of the total IgG.

CONCLUSION

anti-MPO IgG(3) antibody is more closely related with clinical disease activity than the total IgG. Higher ratio of IgG(4) may suggest that chronic repeated antigen stimuli may play a role in the production of ANCA.