Antineutrophil antibodies in vasculitis

Antineutrophil cytoplasm antibodies appear highly specific to the primary systemic vasculitides, in particular to Wegener's granulomatosis and microscopic polyarteritis. Their occurrence in idiopathic crescentic rapidly progressive glomerulonephritis supports the view that this disorder may be regarded as a renal limited form of microscopic polyarteritis. The high sensitivity and specificity of ANCA detected using indirect immunofluorescence or solid phase techniques aids the primary diagnosis of these disorders; the measurement of ANCA may also be of value in long-term monitoring since disease relapse appears to occur only when ANCA are present, and it may therefore be inadvisable to withdraw immunosuppressive treatment until ANCA have been undetectable for extended periods of observation. However, the continued presence or reappearance of ANCA following initial induction of disease remission is not necessarily in concord with overt disease activity, although ANCA has been present in all patients in whom disease relapse has occurred. To understand further the role and relationship of ANCA to the vasculitic diseases requires elucidation of the autoantigen, and in this regard various neutrophil enzymes would appear to be likely candidates. Meanwhile, direct evidence of in vivo pathogenicity and studies of possible mechanisms of tissue injury, such as antiendothelial cell reactivity, are being sought.