One of the most vital functions of the vertebrates is to maintain hemostasis through coagulation and fibrinolysis. This is achieved by the interaction of vascular walls with blood components such as cells and proteins (coagulation factors, immunoglobulins, and complement). Deficiency of coagulation factors results in bleeding disorders. The immune system, in response to foreign proteins or defective self proteins, produces antibodies triggering an Ag-Ab interaction with the related host of different reactions including abnormal coagulation leading to hemorrhagic diathesis.