Factor VIII on the Vascular Intima: Possible Importance in Haemostasis and Thrombosis

Abstract

THE site of factor VIII (anti-haemophilic factor) in tissues is uncertain. Clinical observations have suggested that it is associated with the reticuloendothelial system^1,2 and in experimental studies it has been shown to be released from perfused liver, spleen and kidney^3,4. Pool⁵ detected it only in the spleen by coagulation techniques. It is also thought to be present in cultures of peripheral blood leucocytes and skin fibroblasts^6,7, and factor VIII-like material has been extracted from the kidney⁸. In all these studies factor VIII has been detected by coagulation techniques but the development of immunological methods has offered a potentially more specific and sensitive approach. We have used a factor VIII inhibitor neutralization technique to demonstrate the presence of factor VIII antigen in washed crude homogenates of liver, spleen and kidney⁹. This work has now been extended, by using immunohistological studies with fluorescein-conjugated antisera. These indicate the presence of factor VIII on the vascular intima of many organs and in the mononuclear cells of the spleen. The results may be of importance for studying not only the physiology of haemostasis but also the pathogenesis of thrombosis.