Earth Day 1994

METHODS in somatic cell hybridization, introduced by Kohler & Milstein (1975), have made it possible to produce monoclonal antibodies in tissue culture. Whilst the method has proved entirely successful for the production of antibodies against particulate antigens such as those on the cell surface (Trucco et al., 1978) and viruses (Koprowski et al., 1977), it has only recently been successfully applied to soluble tumour markers such as CEA (Accolla et al., 1979), hCG (Stahli et al., 1980) and alpha-foetoprotein (Tsung et al., 1980). Monoclonal antibodies against CEA are of special interest, since they promise to overcome particular difficulties associated with the antigenic heterogeneity of this glycoprotein (Rogers, 1976). Conventional antisera raised to purified CEA, even after removal of antibodies to known crossreactive antigens such as NCA, contain a mixed population of antibodies (Keep & Rogers, 1979; Rogers & Keep, 1980). Different batches of antisera consequently vary in binding affinity for different forms of CEA or different antigens in the preparation, and this may impair or alter clinical specificity of the CEA assay. Monoclonal anti-CEA on the other hand should be able to discriminate between small antigenic differences expressed by the CEA complex, and provide tools to characterize CEA immunologically, to optimize and stabilize the specificity of the CEA assay and to test the concept that some antigenic