Factor XI Antigen and Activity in Human Platelets

Washed platelets, contaminated with less than 0.20% plasma factor XL were examined for the presence of factor XI antigen and activity. These platelets contained a factor-Xl-like coagulant activity (0.67 ± 0.11 U/1011 platelets) that remained constant after successive washes. By means of indirect imm...

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Bibliographic Details
Published in:Blood 1982-06, Vol.59 (6), p.1148-1156
Main Authors: Tuszynski, George P., Bevacqua, Sandra J., Schmaier, Alvin H., Colman, Robert W., Walsh, Peter N.
Format: Article
Language:English
Subjects:
Antigens - analysis
Blood Platelets - immunology
Blood Platelets - metabolism
Chemical Precipitation
Factor XI - analysis
Factor XI - immunology
Fluorescent Antibody Technique
Humans
Immunoelectrophoresis
Immunologic Techniques
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Summary:Washed platelets, contaminated with less than 0.20% plasma factor XL were examined for the presence of factor XI antigen and activity. These platelets contained a factor-Xl-like coagulant activity (0.67 ± 0.11 U/1011 platelets) that remained constant after successive washes. By means of indirect immunofluorescence, a monospecific antibody to factor XI showed specific staining of both normal platelets and platelets from patients deficient in plasma factor XI. Radiolabeled Triton extracts of washed platelets and labeled purified factor XI solutions were analyzed for factor XI antigen by Staph A immunoprecipitation analysis using antibody to purified plasma factor XI followed by SDS gel electrophoresis. On unreduced gels, the platelet material ran as a single band having an apparent molecular weight of 220.000 daltons, whereas purified plasma factor XI gave a single band at 160,000 daltons. On reduced gels, the platelet material analyzed as a single band at 52,000 daltons, whereas purified factor XI gave a single band of 80,000 daltons. Analysis of a partially purified factor XI preparation from platelets by immunoelectrophoresis revealed that the platelet preparation displayed a slightly lower cathodal electrophoretic mobility at pH 8.6 than did plasma factor XI and yet appeared to possess complete antigenic identity with plasma factor XI. These results indicate that platelets possess a form of factor XI that exists as a disulfide-linked 52,000-dalton tetramer in contrast to the plasma form that circulates as a 80,000-dalton disulfide-linked dimer.
ISSN:0006-4971
1528-0020
DOI:10.1182/blood.V59.6.1148.1148