Long-term treatment results and the immunoglobulin G subclass distribution patterns of proteinase-3-antineutrophil cytoplasm antibody (ANCA) and myeloperoxidase-ANCA in ANCA-associated vasculitis

Objective. Small vessel vasculitis associated with antibodies to neutrophil cytoplasm antigens has been denominated antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV). Material and methods. Ninety-eight patients with various forms of AAV with renal involvement were studied retrospectively with regard to treatment, side-effects and outcome. The immunoglobulin G (IgG) subclass distribution patterns in serum were determined in 51 patients with nephelometry and those of anti-proteinase-3 (PR3) and anti-myeloperoxidase (MPO) in 44 patients by enzyme-linked immunosorbent assay. Results. Fifty-nine patients with a mean age of 63 years were given treatment with intermittent intravenous regimens of cyclophosphamide and continuous corticosteroids, whereas 39 patients with a mean age of 58 years were given continuous oral treatment. Malignancy, mainly due to skin tumours, was more common in AAV than in the general population. The total IgG subclass distribution pattern was asymmetric. The response to PR3 was of IgG1, IgG3 and IgG4 isotypes, while IgG1 and IgG3 predominated in the response to MPO. Conclusion. The aberrant IgG subclass distribution pattern detected in the autoantibodies may be of importance in the pathogenesis of AAV.