IMMUNOLOGICAL HETEROGENEITY OF CARCINOEMBRYONIC ANTIGEN - ANTIGENIC DETERMINANTS ON CARCINOEMBRYONIC ANTIGEN DISTINGUISHED BY MONOCLONAL-ANTIBODIES

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  • 1 January 1983
    • journal article
    • research article
    • Vol. 43  (2) , 686-692
Abstract
Murine monoclonal antibodies against carcinoembryonic antigen (CEA) derived from a [human] colonic tumor were analyzed by radioimmunoassay for reactivity with CEA and the CEA-related antigens, meconium antigen (MA) and nonspecific cross-reacting antigen. Antibody-antigen binding profiles revealed 3 classes of hybridomas. The Class I antibody, NP-1, recognized an epitope shared among all 3 antigens, and its affinity for CEA and MA was high but low for nonspecific cross-reacting antigen. The Class II antibodies reacted with sites shared between CEA and MA, while those of the Class III type only bound CEA. The Class III antibody, NP-4, bound less than 50% of the CEA molecules recognized by goat specific anti-CEA antibody and the other classes of monoclonal antibodies. Two Class II antibodies, NP-2 and NP-3, bound similar amounts of CEA and MA with moderate but different affinities for CEA. Studies using labeled monoclonal antibodies for CEA epitope blocking revealed that NP-2 and NP-3 recognize 2 separate epitopes on CEA within the Class II category. Monoclonal antibodies to CEA can differentiate at least 4 antigenic sites on colonic cancer CEA. One is shared by CEA, MA and nonspecific cross-reacting antigen; 2 others are shared by CEA with MA; and a 4th appears specific for a subpopulation of CEA molecules.