Role of factors XII, XI, and IX in serum and plasma-induced thrombosis

¹ Medical Research Department of the Yamins Research Laboratory, Beth Israel Hospital, and Department of Medicine, Harvard Medical School, Boston, Massachusetts

The possible in vivo relationship between the known coagulation factors and experimental thrombus formation is discussed. A thrombogenic activity can be elaborated in human plasma from inert precursors by exposure of the plasma to a foreign surface. This plasma activity can only induce stasis thrombi when infused into animals that have factor IX (plasma thromboplastin component, PTC). A more potent thrombogenic activity exists in normal human serum, devoid of thromboplastin and thrombin, which cannot be equated with either activated factor XI (plasma thromboplastin antecedent, PTA) or factor IX alone, but which probably represents a combination of both these factors. All recognized clotting factors except factor IX have previously been shown to be distinguished from the thrombogenicity of normal serum. The coagulation of human blood is believed to proceed initially through the sequential activation of factors XII, XI, and IX. The present data, obtained using in vivo thrombus formation as the end point, are consistent with these interpretations of in vitro observations.

Key Words: serum thrombotic accelerator activity • coagulation factors • kinetics of intravascular coagulation

Submitted on May 27, 1963