Carcinoembryonic antigen (CEA) was first described in 1965 by Gold and Freedman'as a high molecular weight glycoprotein found in colonic tumors and fetal colon but not in normal adult colon. Since then the development of sensitive immunoassays for CEA has spurred numerous clinical, immunological, biological, chemical, and physical studies. These studies have revealed that CEA is a member of a complex gene family whose gene products can be found in a variety of tumors as well as normal tissues. In spite of these studies, the biological function of CEA is unknown, the clinical utility of CEA immunoassays is controversial, and the size and relationships of the gene products remain unclear. These apparent contradictory findings have continued to stimulate research on CEA, and as a result of recent breakthroughs in the characterization of CEA by monoclonal antibodies, and the possibility of cloning the gene (s) for CEA, we can expect that many of the questions regarding CEA will be answered in the next 2 to 3 years.

This review is an attempt to summarize some of the most significant aspects of our current knowledge of CEA. The greatest emphasis is placed on important developments in the clinical and immunological studies in the past 2 years. For a historical perspective, the reader is referred to a number of excellent reviews written in the past 10 years.~-~ 2