Tissue factor; from Morawitz to microparticles.

Tissue factor is the principal activator of blood coagulation in vivo. The existence of extravascular tissue factor has been recognized for over a century, but a rational role as a cell-based enzymatic cofactor in blood coagulation was first proposed by Paul Morawitz in 1905. By the close of the last century, very low levels of circulating tissue factor had been identified in the intravascular compartment, but its role in health and in hemostatic and thrombotic disorders continues to be debated. Nonetheless, ongoing research suggests that tissue factor may be a rational therapeutic target in a number of human disease states.