Affinity of myeloma IgG proteins for fibronectin.

The ability of purified human myeloma IgG proteins to interact with human plasma fibronectin was studied by enzyme immunoassays. Seven of eight different myeloma IgG proteins representing all four IgG subclasses bound to solid phase fibronectin in a dose-dependent manner. The binding of myeloma IgG to solid phase fibronectin could be inhibited by soluble fibronectin and gelatin, but not by heparin or bovine serum albumin. Evidence for an antigen-antibody type interaction was not observed by double diffusion analysis. Affinity chromatography of radiolabelled cell culture medium over IgG-Sepharose showed that only fibronectin bound to the IgG-conjugates. The affinity of IgG molecules for fibronectin may play a role in cryoimmunoglobulinaemia associated with certain pathological states.