Heterogeneity of circulating carcinoembryonic antigen analyzed by sandwich-enzyme immunoassays with different specificities.
Nine monoclonal antibodies against carcinoembryonic antigen (CEA) were prepared and used to investigate the immunological and physicochemical heterogeneity of circulating CEA. Two of these, M221-73 and M272-11, recognized "CEA-distinctive" epitopes and they gave sandwich-enzyme immunoassays far less reactive with nonspecific cross-reacting antigen (NCA) and nonspecific cross-reacting antigen-2 (NCA-2). Sandwich-enzyme immunoassays selective for NCA-2 and NCA were also established using suitable monoclonal antibodies as competitive inhibitors against enzyme-labeled antibodies. The studies on the serum CEA levels determined by the "CEA-specific" assay indicated that CEA molecules recognized by M221-73 and M272-11 were generally found in the sera of both cancer patients and normal adults. CEA and related substances in sera were further analyzed by the sandwich-enzyme immunoassays after adsorption on M272-11-coupled immunosorbents and by gel filtration on an Ultrogel AcA-34 column. These studies revealed the presence of a CEA variant detected by the "NCA-2-selective" assay. The variant seemed to be closely related to NCA-2 because it lacked CEA-distinctive epitopes and had an apparent molecular weight similar to that of NCA-2. This variant appeared in the sera of some cancer patients and normal adults.
D000327:Adsorption; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D000951:Antigens, Neoplasm; D002272:Carcinoembryonic Antigen / Q000032:analysis* / Q000276:immunology; D015815:Cell Adhesion Molecules; D002850:Chromatography, Gel; D000939:Epitopes / Q000032:analysis; D005260:Female; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008970:Molecular Weight; D009369:Neoplasms / Q000097:blood
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D002272:Carcinoembryonic Antigen; D015815:Cell Adhesion Molecules; D000939:Epitopes; D006023:Glycoproteins