Biological regulation of factor VIII activity

Factor VIII, the plasma protein deficient in hemophilia A, is a crucial cofactor for regulation of hemostasis. Our understanding of factor VIII increased tremendously once it became possible to isolate homogeneous preparations of this protein from plasma. In addition, the isolation of the factor VIII gene has provided new means of exploring the structure and function of factor VIII. This increasing knowledge also sheds light on the genetic alterations resulting in hemophilia as well as in thrombophilia. This chapter summarizes our current understanding of the regulation of factor VIII function and raises questions to be answered in the years to come.