Competitive enzyme immunoassay for human plasma fibronectin.

A competitive enzyme immunoassay for the determination of fibronectin in plasma is described. An enzyme conjugate prepared by coupling alkaline phosphatase to rabbit anti-human fibronectin antibodies by glutaraldehyde was used as principal reagent. The assay was performed by coating polystyrene tubes with purified fibronectin and reacting these coated tubes with a mixture of sample and enzyme-labeled antibodies. After overnight incubation, the amount of enzyme activity associated with the tube was determined. An assay range of 0.5-20 microgram/ml of fibronectin was obtained. The mean concentration of plasma fibronectin in female patients was found to be 270 microgram/ml (standard deviation 50 microgram/ml, n = 22). Denatured fibronectin had low activity in the assay. The presence of cross-reacting antigens in rat and guinea pig plasma was demonstrated by the enzyme immunoassay technique.