title: Circulating complexes containing IgA and fibronectin in patients with primary IgA nephropathy.
abstract: IgA antibodies from patients with primary IgA nephropathy bind to collagens I, II, and IV. Here we show that this binding is mediated by the collagen-binding site of fibronectin, which occurs in the circulation in complex with IgA. No antibodies binding directly to collagen were identified. The complexes were isolated by affinity chromatography on gelatin-Sepharose and heparin-Sepharose, both with affinity for fibronectin, followed by adsorption to anti-human IgA immobilized on agarose gel. The presence of fibronectin and IgA antibodies in the isolated complexes is shown by enzyme-linked immunosorbent assay, gel electrophoresis, and electrophoretic transfer followed by immunostaining. The presence of an IgA-fibronectin complex in serum and the binding of this complex to collagen demonstrate the necessity of removing fibronectin from serum prior to identifying anti-collagen antibodies.
authors.affiliation: Department of Nephrology, University Hospital, Lund, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Cederholm
authors.forename: J
authors.initials: J
authors.lastname: Wieslander
authors.forename: P
authors.initials: P
authors.lastname: Bygren
authors.forename: D
authors.initials: D
authors.lastname: Heinegård
mesh_terms: D000327:Adsorption; D000918:Antibody Specificity; D000936:Antigen-Antibody Complex / Q000032:analysis*; D001323:Autoantibodies / Q000276:immunology*; D001665:Binding Sites; D002846:Chromatography, Affinity; D003094:Collagen / Q000378:metabolism*; D005353:Fibronectins / Q000276:immunology* / Q000378:metabolism; D005780:Gelatin; D005922:Glomerulonephritis, IGA / Q000276:immunology*; D006493:Heparin; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology* / Q000378:metabolism; D012685:Sepharose
chemical_list: D000936:Antigen-Antibody Complex; D001323:Autoantibodies; D005353:Fibronectins; D007070:Immunoglobulin A; D005780:Gelatin; D006493:Heparin; D003094:Collagen; D012685:Sepharose