Heterogeneity of autoantibodies to factor VIII: differences in specificity
for apparently distinct antigenic determinants of factor VIII coagulant
protein
MP Croissant, M Zuzel and JP Allain
The interference of antibodies to factor VIII coagulant protein (VIII:C) of
9 nonhemophilic patients with the binding to factor VIII coagulant antigen
(VIII:CAg) of a reference hemophilic 125I-Fab' reagent, used in a liquid
phase VIII:CAg assay, was studied. The binding competition was estimated
from immunoradiometric assay (IRMA) dose-response slope of VIII:CAg present
in patient plasma, interference of antibodies with the 125I-Fab' binding to
VIII:CAg in normal plasma, and the displacement of antibody from the
complexes with VIII:CAg by the 125I Fab'. Antibody populations from three
patients were studied in detail; in the VIII:CAg assay, two of them
interfered with the 125I- Fab' binding, and one did not (patient 1). The
formation of stable complexes between antibodies of each patient and
VIII:CAg was demonstrated by protein-A-Sepharose adsorption. The 125I-Fab'
binding to VIII:CAg-anti-VIII:CAg IgG complexes indicated that patient 1
antibodies and the 125I-Fab' recognized different antigenic determinants,
whereas the other two patient antibodies and 125I-Fab' recognized closely
related or identical VIII:CAg determinants. These results demonstrate an
apparently selective recognition of at least two distinct VIII:CAg
determinants by naturally occurring antibodies, suggesting a possibility of
a wider use of these antibodies in studies of the structure and function of
factor VIII.
Volume 62,
Issue 1,
pp. 133-140,
07/01/1983
Copyright © 1983 by The American Society of Hematology
