Anti-carbonic anhydrase III autoantibodies in vasculitis syndrome.

AIM: To identify autoantibodies useful in the diagnosis of primary vasculitides.

METHODS: The presence of antibodies against proteins in the lysate of mouse blood vessels was examined by two-dimensional electrophoresis followed by Western blotting for the pooled serum sample from patients with various forms of vasculitis: polyarteritis nodosa (PAN), microscopic polyangiitis (MPA), Wegener's granulomatosis (WG) and Takayasu's arteritis (TA). Autoantigenicity in patients with vasculitides was examined by Western blotting and enzyme-linked immunosorbent assay (ELISA). Clinicopathological correlations between the positivity of the autoantibodies and clinical status of patients with the vasculitis were examined.

RESULTS: The autoantigen detected in the lysate of pooled sera from patients with vasculitides was identified by mass spectrometry as carbonic anhydrase III (CAIII). ELISA showed significantly higher prevalence of anti-CAIII antibodies in MPA patients (MPA, 11/23 [47.8%]; healthy controls, 2/32 [6.3%]; P < 0.001). Further, anti-CAIII antibody-positive MPA patients had higher vasculitis activity scores compared to anti-CAIII antibody-negative patients, and a weak and not significant negative correlation was observed between anti-CAIII antibody levels and myeloperoxidase - anti-nuclear cytoplasmic antibody (MPO-ANCA) levels. No significant differences were found in anti-CAIII autoantibody levels between MPA and the other primary vasculitides.

CONCLUSION: We found significantly high prevalence of anti-CAIII antibody levels in sera from MPA patients. Although the number of samples available in this study is small and anti-CAIII autoantibodies display weak specificity for MPA, anti-CAIII antibodies may be useful for diagnosing MPA in patients who have no ANCA, as well as for assessing disease activity.