Fibrinogen is a 340 kDa glycoprotein complex secreted primarily by hepatocytes and found in fibroblasts, epithelial cells, and some tumor cells. Fibrinogen functions to prevent excessive bleeding through clotting blood vessels. The conversion of fibrinogen to fibrin is triggered by thrombin cleaving the fibrinopeptides A and B from alpha and beta chains. Fibrinogen is also a component of the extracellular matrix and binds to cell surface molecules of inflammatory cells.