title: Preparation and specificities of antisera to the amino-terminal sequence of the carcinoembryonic antigen.
abstract: A tetracosapeptide (peptide-24) corresponding to the amino-terminal sequence of the carcinoembryonic antigen (CEA) was synthesized and characterized. Antisera were produced to the peptide-24, and a radioimmunoassay was developed utilizing peptide-24 with a tyrosine residue on the amino-terminal end (Tyr-peptide-24). Inhibitions of anti-peptide-24-125I-Tyr-peptide-24 complex formation were done with several preparations of CEA and the normal cross-reacting antigen. The extent of cross-reactivities was low, one CEA preparation requiring a 250-fold molar quantity greater than peptide-24 to obtain the same degree of inhibition. Attempts to degrade the CEAs and normal cross-reacting antigens in order to possibly expose the amino-terminal ends for reactivity with antibody did not result in any great increase in inhibitory capacity. It was concluded that either the conformations of the antigenic determinant(s) of the peptide-24 and of the amino-terminal end of CEA were sufficiently different to result in little cross-reacting antigen are blocked for reactivity with antibody by other portions of the molecule.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D002850:Chromatography, Gel; D003429:Cross Reactions; D007106:Immune Sera / Q000032:analysis; D009369:Neoplasms / Q000276:immunology; D010455:Peptides / Q000276:immunology; D011233:Precipitin Tests; D011817:Rabbits; D011863:Radioimmunoassay
chemical_list: D002272:Carcinoembryonic Antigen; D007106:Immune Sera; D010455:Peptides