EXPRESSION AND LOCALIZATION OF TISSUE FACTOR-BASED PROCOAGULANT ACTIVITY (PCA) IN PIGEON MONOCYTE-DERIVED MACROPHAGES

Monocyte-derived macrophages, focal to initiation and progression of a therosclerosis, have been implicated in thrombotic complication of thi s disease. In the present study we demonstrated tissue factor based pr ocoagulant activity in cultured macrophages from the White Carneau pig eon following endotoxin (1-2 mu g/ml) stimulation. This macrophage pro coagulant activity paralleled activity obtained with pigeon brain homo genate. We used Enzyme-Linked Coagulation Assay (ELCA), an ultrasensit ive microtiter plate assay, io measure procoagulant activity in these cells. Through the use of clotting factors purified from pigeon plasma , procoagulant activity could be detected with as few as 1-3 cells. Ti ssue factor antigen, detected through the use of immunogold labelling in conjunction with a polyclonal antibody which was highly specific to human tissue factor, was distributed uniformly over the plasma membra ne of the endotoxin-stimulated cells. These studies suggest that this procoagulant activity might play an important role in the pathobiology of atherosclerosis in White Carneau pigeons by initiating fibrin poly merization and thus leading to thrombotic complications of the disease .