LACK OF IGA ANTINEUTROPHIL CYTOPLASMIC ANTIBODIES IN HENOCH-SCHONLEINPURPURA AND IGA NEPHROPATHY

To verify whether IgA antineutrophil cytoplasmic antibody (ANCA) repre sents a serologic marker in Henoch-Schonlein purpura (HPS), we examine d sera from 41 patients with the disease. Control sera from 28 patient s with primary IgA nephropathy (IgA-N), 26 IgG-ANCA-positive vasculiti s, and 28 normal controls were also studied. An increased IgA binding to neutrophil cytoplasmic extracts but not to purified ANCA antigens w as found in 12.2-14.6% of HSP patients and in 14.3-21.4% of IgA-N pati ents versus 3.5% of normal controls. IgA binding to neutrophil cytopla smic extracts correlated with serum IgA levels, IgA-rheumatoid factor, and IgA-fibronectin binding capacity. Moreover, low amounts of IgG an d fibronectin were detected as contaminants in neutrophil cytoplasmic extracts and fibronectin could partly inhibit the binding of IgA to '' crude'' extracts. We conclude that IgA-ANCA are neither diagnostically nor immunologically specific in HSP and IgA-N. Several factors presen t in the sera of patients with IgA-related nephropathies seem to contr ibute to the ''false-positive'' IgA-ANCA demonstrable in these patient s. (C) 1994 Academic Press, Inc.