Evidences for the association of blood group determinants with the carcinoembryonic antigen molecule

Abstract

Various A,B,O blood group specificities have been found in carcinoembryonic antigen (CEA) preparations, but it is difficult to ascertain if these determinants are carried by the CEA molecule itself or by a contaminating entity. In order to study this problem, we used a ‘sandwich’ radioimmunoassay in which anti-A, B,H antibodies were coupled to a solid phase and incubated with nonlabelled CEA preparations. The immune complex eventually formed was revealed by 125I-anti-CEA antibodies. The 125I-anti-CEA will be bound to the solid phase only if A,B,O blood group determinants are borne by CEA molecules. If the blood group determinants are associated to a glycoprotein not antigenically related to CEA, no bound radioactivity will be found on the solid phase. Using this ‘sandwich’ RIA, we demonstrated that blood group A antigenic determinants, previously identified in CEA preparations, were truly borne by the CEA molecules and not by a contaminating entity. This method, applied to CEA preparations lacking A activity, allowed one to preclude all possibility of nonspecific adsorption of 125I-anti-CEA on the solid phase and to prove the reliability of such a ‘sandwich’ RIA for the research of the association of A,B,O blood group determinants with the CEA molecules.