The role of fibronectin in the cryoprecipitation of monoclonal cryoglobulins.

We have recently reported that fibronectin is a component of mixed cryoglobulins and is responsible in large part for cryoprecipitate formation. We have now extended our studies to serum cryoprecipitates formed in the presence of monoclonal cryoglobulins in patients with lymphoproliferative diseases in order to investigate for a possibly similar influence of fibronectin on cryoprecipitation. Results have shown that these cryoprecipitates contain fibronectin in proportions varying between 10% and 14% of their total protein content. Furthermore, SDS-polyacrylamide gel electrophoresis revealed that next to the cryoglobulins, fibronectin constitutes the second major component of the cryoprecipitates. Depletion of the sera in fibronectin prior to exposure to 4 degrees C, markedly reduced cryoprecipitation of the cryoglobulins, whereas reconstitution in fibronectin restored it. These studies support and extend our previous findings showing the important influence exerted by fibronectin on the process of immunoglobulin cryoprecipitation.