The role of fibronectin in factor VIII/von Willebrand factor cryoprecipitation

To evaluate the role of fibronectin (Fn) in factor VIII (FVIII) and von Willebrand factor (vWf) cryoprecipitation, factor VIII procoagulant activity, factor VIII coagulant antigen, factor VIII-related antigen and von Willebrand ristocetin cofactor activity were measured in cryoprecipitate and cryosupernatant from normal and Fn-depleted plasmas. Following cryoprecipitation of normal plasmas, most of the FVIII and almost all the FvWf recovered were found with a part of Fn and of fibrinogen in cryoprecipitate. Fn-depleted plasmas prepared either by affinity chromatography on gelatin or by immunoadsorption on monoclonal anti-Fn antibodies behaved differently : although their cryoprecipitate contained normal fibrinogen levels, neither FVIII nor FvWf was precipitated. Experiments performed with Fn-depleted plasma to which purified fibronectin had been added, and samples of plasma with decreased Fn levels (0.01 to 0.2 g/l) suggest that there is a relation between initial Fn level and the extent of FVIII/vWf cryoprecipitation. We conclude that Fn, like fibrinogen, is necessary to induce cryoprecipitation of FVIII/vWf and that an initial plasma level of 0.2 g/l is sufficient to obtain good recovery of FVIII/vWf in cryoprecipitate.