[Isolation of carcinoembryonic antigen]

A method employed in the authors' laboratory for isolating the carcinoembryonic antigen (CEA) from tumours of the entodermal digestive tract and their metastases is described. The main step is fractionation of the preparations obtained by perchloric acid extraction using gel filtration on Sephadex G-200, Sepharose 4 B, and Sepharose 6 B at pH 4.5 and 7.0. The peaks with CEA-specific antigeneity were characterized by the distribution coefficient of the CEA between the mobile and the stationary phases (Kav), and by the relative elution volume (ve/vo). The CEA purified by gel filtration could not reliably be enriched through preparative electrophoresis in Sephadex G-25 gel, polyacrylamide gel or Pevikon powder. The isolation procedures used were compared with those reported in the literature, and the results obtained are discussed.