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[Interaction between fibronectin and aggregated IgG]
The present study shows that plasma fibronectin forms complexes with aggregated human IgG (a model for immune complexes) and that the resulting complexes precipitate spontaneously or after addition of PEG from buffered saline. However, no clearcut interaction was observed in serum or synovial fluid. Two currently-used immune complex assays, the C1q solid phase assay and the conglutinin binding assay in a commercial inhibition variant, were tested as to their reliability in the presence of fibronectin. While the C1q-dependent assay showed low susceptibility to fibronectin, the conglutinin binding assay gave increased immune complex values in the presence of pathological concentrations of fibronectin.
The present study shows that plasma fibronectin forms complexes with aggregated human IgG (a model for immune complexes) and that the resulting complexes precipitate spontaneously or after addition of PEG from buffered saline. However, no clearcut interaction was observed in serum or synovial fluid. Two currently-used immune complex assays, the C1q solid phase assay and the conglutinin binding assay in a commercial inhibition variant, were tested as to their reliability in the presence of fibronectin. While the C1q-dependent assay showed low susceptibility to fibronectin, the conglutinin binding assay gave increased immune complex values in the presence of pathological concentrations of fibronectin.