FACTOR-IX VARIANTS OF HEMOPHILIA-B - EFFECT OF ACTIVATED FACTOR-XI AND THE REACTION-PRODUCT OF FACTOR-VII AND TISSUE FACTOR ON THE ABNORMAL FACTOR-IX MOLECULES

Factor IX from 7 unrelated Hemophilia B patients have been isolated to homogeneity. The abnormal Factor IX proteins from the 7 patients could be separated into 5 distinguishable variants. This was based on appearance of Factor IXa activity and cleavage of the proteins when incubated with activated Factor XI or the reaction product of Factor VII and tissue factor, and by utilizing the ox brain prothrombin time. The five groups could be separated as follows: (1) patient with greatly prolonged bovine thromboplastin time, normal cleavage of the Factor IX protein but absolutely no trace of procoagulant activity upon incubation with activated Factor XI or Factor VII and tissue factor; (2) as (1) but normal bovine thromboplastin time; (3) mildly prolonged bovine thromboplastin time, no procoagulant activity and reduced cleavage rate upon incubation with activators of Factor IX; (4) 2 patients with mildly prolonged bovine thromboplastin time, generation of some Factor IXa like activity (1.7% and 2.5%) and reduced cleavage rate upon incubation with activated Factor XI or Factor VII and tissue factor; and (5) two patients with normal bovine thromboplastin time, normal cleavage and 2.8% and 21% Factor IXa like activity generated with activated Factor XI or Factor VII and tissue factor. © 1979.