The potent serine protease thrombin is able to directly cleave C3 as well as C5 in a dose-and time-dependent manner, leading to biologically active C3a/C5a (44) . In addition to thrombin, investigations by our group indicated proteolytic cleavage of C3 and C5 also by FXa, FXIa and plasmin (35) . Interestingly, FVIII and tissue factor failed to directly interact with C3 and C5 (35) . Furthermore, FXIIa activates the classical complement pathway via C1q. Crosstalk between the lectin pathway and the coagulation cascade has only recently been ascertained by the observation that the complex of FVIII and von Willebrand factor possesses lectin activity (45) .