Competitive enzyme immunoassay for quantification of the cellular form of fibronectin (EDAcFN) in blood samples

A competitive enzyme immunoassay based on the monoclonal antibody DH1 was developed for the quantification of extradomain A (EDA)-containing isoform of cellular fibronectin (cFN). The average EDAcFN concentration in normal plasma was 2.46 micrograms/ml and in serum 0.68 micrograms/ml. Similar results were obtained by gelatin-Sepharose binding and immunoblotting. Studies on the effect of storage of plasma and serum as frozen samples indicated that the amount of EDAcFN decreased rapidly when stored at -20 degrees C. Storage at -70 degrees C resulted in less of a decrease in the concentration of EDAcFN. The method permits the determination of EDAcFN in blood samples from diseases showing increased amounts of the protein at the tissue level.