Isolation of Human Antibodies to Factor VIII

Abstract

The purification of human anti-[factor] VIII: C [factor VIII procoagulant activity] antibodies [Ab] appearing in hemophiliac patients following replacement therapy was achieved using 2 different systems. In a liquid phase system, purified human factor VIII was mixed with Ig[immunoglobulin]G from a hemophilic patient with a high titer Ab. Specific anti-VIII: C Ab were recovered following filtration of the antigen[Ag] complexes on Biogel A-5m, dissociation of complexes at pH 3.5 and final isolation by filtration on Sephadex-G200. In a solid phase system, the same IgG fraction was specifically bound to insolubilized human factor VIII. Purified anti-VIII:C Ab were subsequently recovered by elution of Ag-Ab complexes with MgCl2 anti-VIII:C Ab and the whole factor VIII molecule or VIII:C dissociated by previous interaction with the Ab. In vivo, similar Ag-Ab complexes may form following replacement therapy in hemophilic patients with Ab.