Serum IgA-fibronectin aggregates in patients with IgA nephropathy and Henoch-Schönlein purpura: diagnostic value and pathogenic implications. The Glomerular Disease Collaborative Network.
IgA nephropathy is a common form of glomerulonephritis that has varied clinical expressions, ranging from asymptomatic hematuria to rapidly progressive nephritis. We report the strong association (P less than 0.0001) of circulating IgA-fibronectin aggregates with IgA nephropathy. Of 30 patients with IgA nephropathy, 93.3% had serum IgA-fibronectin aggregates detected with an enzyme immunoassay using collagen as a substrate to bind the aggregates. Among the patients with IgA-fibronectin aggregates were patients with Henoch-Schönlein purpura and recurrent crescentic IgA nephropathy in transplants. Only 11.7% of 103 patients with other types of glomerular disease and 6.7% of normal controls had positive IgA-fibronectin aggregate assay levels. IgA-fibronectin aggregates also were detected in serum using an antifibronectin antibody capture assay; and could be depleted from serum by heparin-agarose affinity chromatography. The circulating IgA-fibronectin aggregates had the same unusual predominance of lambda relative to kappa light chains that is observed in the glomerular deposits of IgA nephropathy. The data indicate that IgA-fibronectin aggregates are a useful serologic marker for IgA nephropathy, Henoch-Schönlein purpura, and recurrent IgA nephropathy in transplants. The presence of fibronectin in the circulating aggregates may play an important role in the preferential deposition of nephritogenic IgA-containing immune complexes in the mesangium of patients with IgA nephropathy.
Department of Pathology, School of Medicine, University of North Carolina, Chapel Hill 27599.
J C
JC
Jennette
J
J
Wieslander
R
R
Tuttle
R J
RJ
Falk
D000936:Antigen-Antibody Complex / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005353:Fibronectins / Q000378:metabolism*; D005921:Glomerulonephritis / Q000097:blood / Q000276:immunology; D005922:Glomerulonephritis, IGA / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D006801:Humans; D011695:IgA Vasculitis / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D007070:Immunoglobulin A / Q000097:blood*
D000936:Antigen-Antibody Complex; D005353:Fibronectins; D007070:Immunoglobulin A