Carcinoembryonic antigen - immunochemistry, physical chemistry and clinical implications

The carcinoembryonic antigen (CEA) is a glycoprotein constituent of entodermally derived human digestive organ cancers, and is found in the digestive system of the human embryo and fetus during the first 2 trimesters of gestation. CEA, a glycocalyceal component, is released into the circulation of patients bearing digestive system cancers, where it may be detected by means of a radioimmunoassay. Studies performed to date suggest that radioimmunoassay for CEA may serve as a useful adjunct in the diagnosis and prognosis of patients with cancers of the digestive system and other organs. CEA evokes a humoral, tumor specific antiCEA antibody response in the patient, but does not appear to be involved in stimulating cell mediated immunity. Although purified CEA preparations appear to be homogeneous when studied by ultracentrifugation and immunoprecipitation in gel media, a number of other chemical, physical and immunochemical studies suggest some degree of intermolecular heterogeneity between and within purified preparations of CEA. In addition, evidence has accumulated which suggests intramolecular heterogeneity of the CEA molecule. Investigations of the structure of the immunodominant tumor grouping of the CEA moiety indicate an intimate involvement of the heterosaccharide portion of the molecule.