Detection and quantitation of anti-neutrophil cytoplasm antibodies in Wegener's granulomatosis by ELISA using affinity-purified antigen

Autoantibodies directed against cytoplasmic components of neutrophil granulocytes and monocytes (ACPA) have previously been described as a disease-specific marker for Wegener's granulomatosis (WG). We have developed an ELISA for determining and quantifying ACPA using an affinity-purified antigen preparation. The antigen was purified from supernatants of human neutrophils stimulated with phorbol ester to induce degranulation, by means of affinity chromatography with naturally occurring human autoantibodies. The established ELISA was sufficiently specific and sensitive, and the ACPA concentrations obtained with it correlated significantly with the ACPA titres determined by an indirect immunofluorescence technique (Spearman's rank correlation coefficient = 0.85, P < 0.001, n = 105 WG patients). This ELISA provides precise ACPA quantification and should prove valuable for monitoring disease activity in WG.