title: The abnormal factor IX of hemophilia B+ variants.
abstract: A rather large proportion of the hemophilia B patients can be characterized as hemophilia B+ because of the presence in their plasma of a protein which is immunologically identical with human factor IX. In a group of 33 hemophilia B patients we found 14 cases of hemophilia B+ belonging to 11 independent pedigrees. The variant factor IX molecules of these families have been compared with respect to the following properties: 1) factor IX activity and its dependence on phospholipid concentration; 2) factor IX antigen; 3) prolongation of prothrombin time with an ox brain thromboplastin; 4) electrophoretic mobility; 5) Ca(+) binding capacity; 6) affinity for binding to heparin and 7) susceptibility of the factor IX antigen to contact-induced activation. In the study of these parameters the use of a precipitating antibody against highly purified human factor IX showed to be of great value. According to our criteria at least 7 different factor IX variants were present in the 11 families with hemophilia B+ studied. Because of this rather high heterogeneity a suitable nomenclature for subclassification of hemophilia B+ variants is proposed.
mesh_terms: D000941:Antigens; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D005164:Factor IX / Q000276:immunology / Q000302:isolation & purification; D014644:Genetic Variation; D002836:Hemophilia B / Q000097:blood*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007123:Immunoelectrophoresis, Two-Dimensional; D010743:Phospholipids / Q000378:metabolism
chemical_list: D000941:Antigens; D010743:Phospholipids; D005164:Factor IX; D006493:Heparin; D002118:Calcium