This antibody reacts with human von Willebrand factor. Traces of
contaminating antibodies have been removed by solid-phase absorption with human
plasma proteins. This protein has functional binding domains to platelet
glycoprotein Ib, glycoprotein IIb/IIIa, collagen and heparin. The Factor VIII
(Von Willebrand Factor) is synthesized by endothelial cells and stored in the
Weibel-Palade granules. This antibody reacts specifically with the endothelial
cells of both normal and reactive, and neoplastic blood and lymphatic vessels
and a finely granular cytoplasmic staining. It also reacts with endocardium,
platelets, and megakaryocytes. Factor VIII has been shown most useful in marking
and identifying normal endothelial cells of their corresponding neoplasms.
However, because not all endothelial cells synthesize and/or store the molecule,
this antibody will mark approximately 70% of tumors of vascular origin. It is
therefore recommended that both CD34 and Factor VIII be used together as a
panel. Staining for factor VIII related antigen has also been used to measure
angiogenesis and has been shown in some studies to predict tumor
recurrence.