Immunochemical identification of an α1-acid glycoprotein-antigenic determinant on carcinoembryonic antigen (CEA) and non-specific cross-reacting antigen (NCA)

Abstract An immunochemical characterization of carcinoembryonic antigen (CEA) and NCA (non-specific cross-reacting antigen) was performed. Positive reactions of CEA and NCA ( M r 60000) with some antibodies to α 1 -acid glycoprotein (AG) were observed. Thus, both antigens may contain immune determinants in common with α 1 -acid glycoprotein. CEA showed positive reactivity with anti-NCA. NCA showed positive reactivity with either polyclonal or monoclonal antibodies to CEA, but negative reactivity with auto-antibodies to CEA. 125 I-Tetracosapeptide (synthetic peptide-24 corresponding to the amino terminal sequence of CEA) failed to react with any antisera against CEA, NCA and AG. 125 I-AG also showed no immuno-reaction with any antibody against CEA, NCA and tetracosapeptide. These results suggest that some monoclonal antibodies to CEA are directed against a common antigenic determinant of both CEA and NCA in addition to AG