Isolation and characterization of a homogeneous isomeric species of carcinoembryonic antigen: CEA‐S

Publisher Website
Google Scholar
Abstract
A single homogeneous isomeric species of carcinoembryonic antigen was isolated by reference to solubility in 0.9 M perchloric acid, isoelectric focusing, molecular exclusion chromatography, ion exchange chromatography, passage through immunoabsorbants, and isopyknic density gradient ultracentrifugation. The final product, representing approximately 1.8% of the perchloric acid soluble glycoprotein of the tumor, is homogeneous and devoid of other proteins by polyacrylamide gel electrophoresis. This single species of carcinoembryonic antigen, CEA‐S, has a sedimentation velocity of 6.6, a diffusion constant of 3.05 × 10−7 cm2/sec, a mean Stokes radius of 65 Å, a density of 1.41 ml/g in cesium chloride and an estimated molecular weight of 181,000, and it is devoid of detectable A or B blood‐group antigens. Immunochemical studies demonstrate qualitative similarities between CEA‐S and conventional carcinoembryonic antigens; however, competitive inhibition analyses demonstrate significant quantitative immunochemical differences between CEA‐S and preparations of carcinoembryonic antigen. These results are consistent with the concept that CEA‐S is an immunochemical isomer of carcinoembryonic antigen.