[The role of sugar chains in the antigenicity of CEA molecule]

CEA is a glycoprotein with a molecular weight of about 180,000, 60% of which is composed of carbohydrate. Recent findings were summarized on the antigenic structure, the primary structure of peptide, the membrane anchoring device on the sugar chain structure of CEA. Although CEA molecule possesses 24 approximately 26 asparagine-linked sugar chains, which seem to cover uniformly the peptide core chain, antigenicity of sugar chains themselves is rather weak. Sugar chains were found, however, to have profound effects on the antigenicity of CEA peptide. Thus, many peptide epitopes may be buried by sugar chains, and estimations of serum CEA titers were influenced by heterogeneity and instability of sugar chain structures of CEA in test sera. A monoclonal assay system for CEA was established, which seemed almost independent of sugar chain heterogeneity, and showed definite improvements in cancer specificity, sensitivity and accuracy.