An immunoradiometric assay for human factor VIII/von Willebrand factor (VIII:vWF) using a monoclonal antibody that defines a functional epitope.
A murine monoclonal antibody has been produced (RFF-VIII:R/2) that binds specifically to human factor VIII-related antigen (VIII:RAg) in plasma and in vascular endothelial cells but has no reactivity with factor VIII procoagulant antigen (VIII:cAg). This antibody is a potent inhibitor of von Willebrand factor activity (VIII:vWF) in that it can totally neutralize ristocetin-induced aggregation of platelet rich plasma and inhibit platelet adhesion at high flow rates. RFF-VIII:R/2 can be used in a one-stage, fluid phase immunoradiometric assay that can detect VIII:RAg at concentrations of 0.001 u/ml. This method has been used to analyse plasma from patients with von Willebrand's disease (vWD). Results obtained in these patients showed a high degree of correlation between the monoclonally-defined epitope and VIII:vWF levels measured by ristocetin-induced aggregation of washed platelets. This correlation was maintained in those patients with the 'variant' types of vWD who exhibit highly disparate VIII:vWF and VIII:RAg levels when the latter is determined using polyclonal antisera. It appears that this monoclonal antibody recognizes a site on the VIII:RAg molecule which is associated with its interaction with the platelet membrane. Immunoradiometric assays using RFF-VIII:R/2 offer a simplified, reproducible means of detecting functionally-active VIII:RAg as an alternative or supplement to techniques involving platelet interactions.
Goodall
A H
AH
Jarvis
J
J
Chand
S
S
Rawlings
E
E
O'Brien
D P
DP
McGraw
A
A
Hutton
R
R
Tuddenham
E G
EG
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000941:Antigens / Q000276:immunology; D001779:Blood Coagulation Factors / Q000032:analysis*; D000939:Epitopes / Q000276:immunology; D005169:Factor VIII / Q000032:analysis* / Q000276:immunology; D006801:Humans; D051379:Mice; D010974:Platelet Aggregation / Q000187:drug effects; D011863:Radioimmunoassay; D012310:Ristocetin / Q000494:pharmacology; D014842:von Willebrand Diseases / Q000097:blood*; D014841:von Willebrand Factor / Q000032:analysis* / Q000276:immunology
D000911:Antibodies, Monoclonal; D000941:Antigens; D001779:Blood Coagulation Factors; D000939:Epitopes; D014841:von Willebrand Factor; D012310:Ristocetin; D005169:Factor VIII