Cellular fibronectin in plasma: its implications in fibrinogen-associated cryoprecipitation and other related reactions.

Elimination of cryoprecipitable plasma components (cryogels) by cryofiltration from the circulating blood of patients with drug-resistant rheumatoid arthritis (RA) alleviates clinical symptoms including morning stiffness and arthralgia. The cryogels thus isolated from the blood were found to consist mainly of fibrinogen (Fbg) and fibronectin (FN). Analysis by immunoblotting with an anti-cellular FN monoclonal antibody revealed that cellular FN (cFN) co-existed with plasma FN (pFN) in the cryogels derived from the patients. Using an ELISA, we assessed cFN together with the total FN (pFN+cFN) in plasmas and cryogels derived from the patients. The cFN/total FN ratio was distinctly higher in the cryogels than in the plasmas, suggesting that cFN was more readily precipitated than pFN in association with Fbg under cold conditions.