The nature of the AHF/vWF complex in plasma, cryoprecipitate, or intermediate purity
concentrate has been the subject of intensive study. Some investigators have felt
that it was a single molecule with at least two activities; others have thought that
it was made up of two noncovalently bound molecules, partially separable by Sepharose
chromatography or ultra-centrifugation in high ionic strength NaCl or CaCl2, or by interaction with specific antibodies. Our data indicate that AHF from human,
porcine or bovine plasma, human cryoprecipitate, or intermediate purity AHF concentrates
may be quantitatively separated from vWF by adsorption of the AHF on solid-phase maleic
anhydride copolymer resins; most of the AHF may be eluted from the resin by a high
concentration of salt while virtually all the vWF remains in the supernatant; the
separation is unaffected by usual concentrations of protease inhibitors (DFP, 1mM)
benzamidine (1mM), PMSF (1 mM) or trasylol (10-100 KIU/ml). One adsorption changes
the ratio of AHF/vWF units in plasma from 1:1 to approximately 200:1; after two adsorptions
the ratio is approximately 1500:1. AHF dissociated from vWF assays the same by one
and two stage assays, is neutralizable by specific homologous antibody and is activatable
by thrombin. When vWF in cryoprecipitate was separated from AHF by adsorption of the
AHF on PE, the ratio of vWF to AHF was 200:1. At concentrations greater than 0.1 units/ml,
vWF levels, as assayed by the ristocetin cofactor assay, were comparable to results
obtained by the RIA of Hoyer, and the solid-phase radio-immunoassay of Ruggieri. These
data are consistent with a non-covalent AHF/vWF complex made up of two different molecules
which may be separated readily by adsorption on solid-phase PEs.