Production and characterization of monoclonal antibodies to N-domain and domain III of carcinoembryonic antigen.

In order to obtain MoAbs against N-domain or domain III of carcinoembryonic antigen (CEA), mice have been immunized with a recombinant deleted CEA which was devoid of most of domains I and II. Of the nineteen MoAbs established, ten MoAbs were reactive with the N-domain of CEA, and others recognized the domain III. All Fab fragments of the MoAbs against the N-domain significantly inhibited homophilic cell adhesion mediated by CEA, whereas that of normal mouse IgG or control MoAb (anti-HLA class II) did not. Among the Fab fragments of MoAbs against the domain III, three inhibited the cell adhesion slightly, while five enhanced and one had no effect. These findings suggest that the N-domain of CEA plays an important role in the cell adhesion, and that the domain III is also involved in the binding. The MoAbs described in this study will be useful to elucidate the functional roles of the domains of CEA molecule.