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[Cancer Research 35, 1804-1808, July 1, 1975]
© 1975 American Association for Cancer Research
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The Binding of Carcinoembryonic Antigen by Antibody and Its Fragments1

James E. Morris2, Marianne L. Egan and Charles W. Todd

Department of Immunology, City of Hope National Medical Center, Duarte, California 91010

In order to assess the potency of antigenic fragments of carcinoembryonic antigen (CEA) in the radioimmune assay, it is necessary to know whether the high affinity of goat anti-CEA antibody (which makes possible the detection of as little as 10-11 M CEA) is due to bivalent binding of the CEA molecule. Immunoglobulin G and the F(ab')2 and Fab' fragments derived from it were prepared from an anti-CEA serum and tested for their ability to bind CEA. Equivalent concentrations of binding sites of the bivalent F(ab')2 and univalent Fab' fragments of anti-CEA were identical to the immunoglobulin G fraction in the standard inhibition curve. Fragments of CEA obtained by trypsin digestion produced equivalent inhibition curves when tested with either immunoglobulin G, F(ab')2, or Fab'. Thus, increased avidity due to bivalent binding to a single antigen molecule cannot be invoked to explain the sensitivity observed in the CEA assay. This high sensitivity implicates the protein rather than the carbohydrate as an important part of the antigenic determinant(s) of CEA.

1 Supported in part by Grant IC-44 from the American Cancer Society and Grant CA 12631 from the National Cancer Institute, by Contract N01 CB23877 with the National Cancer Institute, and by the Stuart L. Bernath Cancer Research Fund.

2 Present address: Biology Department, Battelle Pacific Northwest Laboratory, Richland, Wash. 99352.

Received 12/ 9/74. Accepted 4/ 3/75.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Cancer Research Clinical Cancer Research
Cancer Epidemiology Biomarkers & Prevention Molecular Cancer Therapeutics
Molecular Cancer Research Cancer Prevention Research
Cancer Prevention Journals Portal Cancer Reviews Online
Annual Meeting Education Book Meeting Abstracts Online
Copyright © 1975 by the American Association for Cancer Research.