INCIDENCE AND STUDIES ON ANTIGENIC SPECIFICITIES OF ANTINEUTROPHIL-CYTOPLASMIC AUTOANTIBODIES (ANCA) IN POSTSTREPTOCOCCAL GLOMERULONEPHRITIS

Sera from 210 patients with Acute Poststreptococcal Glomerulonephritis (APSGN) and 14 patients with streptococcal impetigo without glomerula r disease were tested for the presence of IgG-ANCA using an indirect i mmunofluorescence assay (IIF) on ethanol fixed normal human neutrophil s. In the group of nephritic patients, ANCA were detected by IIF in 9% (18 out of 210 cases) in an atypical diffuse cytoplasmic pattern (a-A NCA) in 14 cases and in a (p-ANCA) perinuclear staining in the remaini ng 4 cases. Longitudinal studies performed on six IIF positive patient s, showed persistence of the phenomenon for up to six months, without relationship with activity of disease. No patient with streptococcal i mpetigo showed positivity on the IIF assay. Positive sera were analyze d on ELISA plates for their IgG reactivity against specific purified A NCA antigens: Proteinase-3 (PR3), Myeloperoxidase (MPO), Cathepsin-G a nd Bactericidal/Permeability Increasing Protein (BPI). Anti-MPO antibo dies were present in 4 cases (3 a-ANCA and 1 p-ANCA). No reactivity wa s identified against PR-3, BPI and Catepsin-G in any of the samples. T he presence of ANCA was significantly associated with a more severe gl omerular disease as assessed by the serum creatinine and the crescents formation. Further studies are required to identify other antigenic s pecificities of these autoantibodies. Their absence in the streptococc al impetigo control group might suggest that their presence in APSGN c ould play some pathogenic role in kidney disease.