The general objective is to define the antigenic profile and immunochemical characteristics of carcinoembryonic antigen (CEA) of the human digestive system and to study the interrelationships of CEA, nonspecific cross-reacting antigen (NCA), and two CEA-related meconium antigens. Using antibodies isolated from conventional antisera against unique and common specificities on CEA, the immunochemical nature of CEA appearing in plasma and tissue from normal individuals and patients with malignant and nonmalignant gastrointestinal disease will be characterized according to size and lectin binding properties. The physicochemical, immunochemical, and tissue specificity properties of the CEA-like meconium antigens will be determined and compared to those of CEA and NCA. The interrelationships in the expression of CEA and CEA-like antigens will be studied in plasma and tissue specimens. Murine monoclonal antibodies will be developed against CEA obtained from colonic and gastric cancer as well as against the CEA-like antigens to define further the antigenic specification of CEA and related antigens. A clearer definition of the immunochemical profile of CEA and related antigens would allow a more complete understanding of their interrelationships and provide opportunities to evaluate them with regard to tissue specificity, response to therapy, patient survival, and cancer cell evolution. (2)