Characterization of procoagulant activity produced by cultures of human monocytes and lymphocytes separated in colloidal silica‐polvinylpyrrolidone gradients

Human peripheral blood leucocytes were examined for their ability to synthesize procoagulant activity in tissue culture. A method was developed utilizing silica coated with polyvinylpyrrolidone (Percoll) to separate monocytes from lymphocytes prior to culture. Coagulation activity was demonstrated in all mononuclear cell cultures after 24 hours incubation. This activity was inhibited by phospholipase C which suggested that tissue thromboplastin was the major source of activity. Specific immunoradiometric assays failed to demonstrate synthesis of factor VIII related antigen (FVIIIRAG) or factor VIII coagulant antigen. The results indicate that under conditions of this study factor VIII was not synthesized in mononuclear cell cultures.