The monoclonal antibody clone CLB/TF-5 recognize human soluble tissue factor (also known as coagulation factor III, tissue thromboplastin or CD142). This protein activates the blood clotting system by binding to, and activating, the plasma serine protease, factor VIIa, following vascular injury. Unlike the other cofactors of these protease cascades, which circulate as nonfunctional precursors, this factor is a potent initiator that is fully functional when expressed on cell surfaces. There are 3 distinct domains of this factor: extracellular, transmembrane, and cytoplasmic. Because of its essential role in hemostasis, tissue factor plays a role in pathology associated with hemostasis, triggering the coagulation system in many thrombotic diseases and the coagulopathies associated with sepsis and other forms of disseminated intravascular coagulation. Recent research has also implicated tissue factor in a variety of nonhemostatic roles, including cell signaling, inflammation, vasculogenesis, and tumor growth and metastasis.