Separation of plasma fibronectin from associated hemagglutinating activity by elution from gelatin-agarose at pH 5.5

Human plasma fibronectin prepared by elution of the adsorbed protein from gelatin-agarose by pH 5.5 citrate buffer is very low in hemagglutinating activity toward trypsinized rabbit erythrocytes, an activity previously associated with the purified plasma protein. Hemagglutinating activity is present, however, in a subsequent fibronectin-poor 4M urea eluate which contains plasma immunoglobulins and/or other unidentified gelatin-binding proteins. This activity is partially inhibited by antibodies to human immunoglobulins, and the inhibition is reversed by excess non-specific human immunoglobulin.