Properties of the Platelet Retention (von Willebrand) Factor and Its Similarity to the Antihemophilic Factor (AHF)

The abnormal retention of platelets in glass-bead filters in von Willebrand’s disease was corrected by a fraction of normal cryoprecipitate that eluted, along with antihemophilic factor (AHF), in the void volume after chromatography on Bio-Gel 5 M. This platelet retention factor had an apparent molecular weight in excess of 5 x 10⁶, was also present in hemophilic cryoprecipitate, but was not detectable in the void volume fractions of cryoprecipitate prepared from the plasma of a patient with von Willebrand’s disease. The adsorptive and thermal stability properties of the retention (von Willebrand) factor were similar to those of AHF. Platelet retention is the result of a complex interaction between red cells, platelets, and the von Willebrand factor, and it is suggested that the activity of the latter factor may be associated with the same high molecular weight protein that possesses coagulant (AHF) activity in normal subjects but that lacks this activity in hemophiliacs. The deficiency of this protein in von Willebrand’s disease may account for the hemostatic defect in this disorder.