Tissue factor (TF), a transmembrane surface protein, is known to initiate thrombogenesis through plasmatic and cellular activation processes. Besides complexing with factor VII, eventually leading to fibrin generation via the extrinsic pathway, TF can also activate factor IX, resulting in the intrinsic activation of coagulation. Other functions of TF are currently unknown, although various cells are believed to have TF receptors. Many of the post-surgical and post-interventional thrombotic events are due to the release of TF. Increased levels of TF are associated with several pathologic conditions such as cancer, sepsis and inflammation. Cellular necrosis also results in an increase of TF as the cells in the traumatized area lyse and release endogenous cell surface-bound TF. An ELISA method (American Diagnostica, Greenwich, CT) has been developed to assay TF antigen levels in various biological fluids. This ELISA employs a murine monoclonal antibody raised against native human TF for antigen capture. In this study, cerebrospinal fluid, peritoneal fluid, pleural effusion and urine from patients were assayed for their TF content using this ELISA method. Normal individual serum and plasma were also assayed as controls against which the levels of TF in the patients' body fluids could be compared. The amount of TF antigen in normal human plasma and serum was 165 +/- 139 pg/ml and 165 +/- 110 pg/ml, respectively. Concentrations of TF antigen in other fluids were: cerebrospinal fluid 868 +/- 721 pg/ml, peritoneal fluid 124 +/- 247 pg/ml, pleural effusion 385 +/- 569 pg/ml, synovial fluid 97 +/- 23 pg/ml, seminal plasma 11,485 +/- 875 pg/ml and urine 86 +/- 57 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)