Summary
Monocyte-derived macrophages, focal to initiation and progression of atherosclerosis,
have been implicated in thrombotic complication of this disease. In the present study
we demonstrated tissue factor based procoagulant activity in cultured macrophages
from the White Carneau pigeon following endotoxin (1-2 μg/ml) stimulation. This macrophage
procoagulant activity paralleled activity obtained with pigeon brain homogenate. We
used Enzyme-Linked Coagulation Assay (ELCA), an ultrasensitive microtiter plate assay,
to 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. Tissue 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 membrane 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 polymerization and thus leading to thrombotic complications of the disease.