The significance of fibronectin in cryoprecipitation in rheumatoid arthritis and other diseases.

Fibronectin, a glycoprotein produced by mesenchymal cells, was present in 11 of 16 plasma cryoprecipitates and 12 of 14 synovial fluid (SF) cryoprecipitates. In some SF cryoprecipitates it was the major protein component. Fibronectin levels were related to the development of serum turbidity in the cold and fibronectin was involved in the development of cold turbidity induced by some charged polysaccharides in plasma, serum, and SF. It is suggested that fibronectin, which is synthesized by vascular endothelial cells and synovial lining cells, is involved in the development of some cryoprecipitates in patients with rheumatoid arthritis and other diseases.