Bruce Bennett

Immunologic Studies in von Willebrand's Disease: EVIDENCE THAT THE ANTIHEMOPHILIC FACTOR (AHF) PRODUCED AFTER TRANSFUSIONS LACKS AN ANTIGEN ASSOCIATED WITH NORMAL AHF AND THE INACTIVE MATERIAL PRODUCED BY PATIENTS WITH CLASSIC HEMOPHILIA

Antihemophilic globulin (AHF, factor VIII) levels were measured by a standard coagulation assay and by an immunological technique before and serially after infusion of fresh frozen plasma or cryoprecipitate into patients with von Willebrands disease. Initial levels of AHF, measured both as procoagulant and as antigen, were low. Immediately after transfusions, the rise in levels of AHF-like antigen was compatible with the quantity of antigen present in the infused plasma or cryoprecipitate. Thereafter, levels of antigen declined rapidly and reached preinfusion values in approximately 24 hr. In contrast, procoagulant activity remained elevated, and sometimes continued to rise, for longer periods of time. One possible explanation of this finding is that the AHF molecule produced by patients with von Willebrands disease, in response to transfusion of as yet unidentified factors, lacks the antigenic site associated with the normal AHF molecule or the inactive molecule produced by patients with hemophilia A.

Detection of the Carrier State for Classic Hemophilia

Abstract Carriers of classic hemophilia may be detected by comparison of levels of antihemophilic factor as measured by clot-promoting assay (i.e., functionally active factor) and by quantitative immunoelectrophoresis (i.e., both functionally active and inactive factor). This technic has detected over 90 per cent of a group of known carriers. In addition, when applied to a group of 18 daughters of known carriers of hemophilia, the technic detected the carrier state in nine of these. In a second group of women, the mothers of hemophilic sons with no family history of the disorder, seven of 10 had evidence of the carrier state. Study of other members of these families suggested that mutation to the abnormal allele occurred on the X chromosome from which either the hemophilic patient or his mother arose.

Studies on the Response of Patients with Classic Hemophilia to Transfusion with Concentrates of Antihemophilic Factor A DIFFERENCE IN THE HALF-LIFE OF ANTIHEMOPHILIC FACTOR AS MEASURED BY PROCOAGULANT AND IMMUNOLOGIC TECHNIQUES

Antihemophilic factor (AHF, factor VIII) levels were measured by a standard coagulation method and by an immunologic technique before and after infusion of AHF concentrates into patients with classic hemophilia. After infusion of AHF concentrates, the half-life of the AHF procoagulant (i.e., clot-promoting) activity varied from 12 to 14 hr, whereas that of the antigen ranged from 24 to 40 hr. The half-life of the antigen was similar in patients with and without circulating anticoagulants to AHF. The data are compatible with the suggestion that the antigen may be carried on a precursor molecule which the patient with hemophilia produces but cannot convert to the functional clot-promoting agent. Other explanations of the observations are, however, recognized.

Studies on the Nature of Antihemophilic Factor (Factor VIII): FURTHER EVIDENCE RELATING THE AHF-LIKE ANTIGENS IN NORMAL AND HEMOPHILIC PLASMAS

Normal human antihemophilic factor (AHF, factor VIII) and the protein antigenically related to it in hemophilic plasma both appeared in the void volume of columns of agarose (Sepharose 4B) during purification of these agents. On ultracentrifugation upon sucrose gradients, both agents had sedimentation characteristics similar to those of an S30 marker. After reduction, the polypeptide chains of purified normal AHF and of the nonfunctional agent from hemophilic patients had an apparent molecular weight of 200,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. These observations suggest that AHF, purified as described, exists as a large molecule with subunits of molecular weight of approximately 200,000. Antisera to normal AHF and the nonfunctional agent from hemophilic plasma appeared to be directed against antigens of similar electrophoretic mobility and precipitating characteristics, present in normal and hemophilic plasma but deficient in severe von Willebrands disease plasma. Both antisera neutralized the AHF clot-promoting activity present in normal plasma, and this property was removed by absorption of the antisera with concentrates of normal or hemophilic plasma but to a greatly reduced extent by concentrates of von Willebrands disease plasma. These findings suggest that the antigen detected in normal plasma by the antisera appears on a molecule participating in the AHF clot-promoting reaction.

Immunologic Relationships of Antihemophilic Factor of Different Species Detected by Specific Human and Rabbit Antibodies

Summary The plasmas of 14 nonhuman mammalian species corrected the specific clotting defect in human hemophilic plasma. The antihemophilic factor (AHF, Factor VIII) activity in all these plasmas was inhibited by human circulating anticoagulants directed against AHF and, except for rabbit AHF, by rabbit antiserum to purified normal human AHF, but human AHF was more readily inhibited than animal plasmas by both these agents. Porcine AHF was more resistant than bovine AHF to inhibition by all of 6 human circulating anticoagulants. In immuno-precipitation studies using rabbit antiserum, primate plasmas gave reactions of identity with human plasma, while non-primate mammalian plasmas gave reactions of partial identity. Plasma from a reptile and from two avian species contained no detectable antigen or clot-promoting properties related to human AHF.

The Differential Effect of Acetylsalicylic Acid on in vitro Aggregation of Platelets from Normal, Asthmatic and Aspirin-Sensitive Subjects

In vitro studies of the effect of acetylsalicylic acid on the collagen-induced aggregation of human platelets are reported. It was found that collagen-induced platelet aggregation w