A REFERENCE OF THE GOLD CLASSIFICATION OF MONOCLONAL-ANTIBODIES AGAINST CARCINOEMBRYONIC ANTIGEN TO THE DOMAIN-STRUCTURE OF THE CARCINOEMBRYONIC ANTIGEN MOLECULE

The epitopes of 42 well-characterized monoclonal antibodies (MAbs) aga inst carcinoembryonic antigen (CEA) from 10 different research groups were mapped in terms of domain structure (domains N, A1-B1, A2-B2, and A3-B3) of the CEA molecule on the basis of the reactivities with reco mbinant CEA proteins expressed in Chinese hamster ovary cells, Thirty- six of the 42 MAbs tested have previously been classified into 5 essen tially nonoverlapping epitope groups (GOLD 1-5) by cross-competition a ssays among MAbs for CEA binding (Hammarstrom S, et al. Cancer Res, 19 89; 49:4852-4858), The epitopes recognized by GOLD 2 MAbs were all pre sent on domain A2-B2, those for GOLD 5 MAbs were all on domain N, and those for GOLD 4 were mapped around domains A1-B1 and A2-B2, On the ot her hand, the epitopes for GOLD 1 MAbs were distributed into domains N , A2-B2, and A3-B3, and those for GOLD 3 MAbs were separated into doma ins N and A3-B3, Although the exact reasons for the dispersed patterns of GOLD 1 and 3 MAbs on the domain structure of the CEA molecule are unclear at present, several factors, such as a spatial relation or a c lose proximity of epitopes, conformation dependency, and repetivity of epitopes, may be considered as possible explanations, The epitope map ping reported here helps form the basis for understanding the relation between the chemical structure and antigenic activities of the CEA mo lecule and may be useful to study the functions of the CEA molecule, e specially those of the respective domains.