Antibody response to different determinants on carcinoembryonic antigen (CEA).

Studies on the diverse nature of the immune response of animals to different antigenic determinants on CEA indicate that the type of antiserum used is of prime importance in determining differences or identities between antigens isolated from tumour and normal tissues. One type of antiserum against CEA shows cross-reactions with a normal colon antigen (NCA) found in both malignant and normal tissues. This finding confirmed that a common determinant is shared by both CEA and NCA. A second type of anti-CEA did not cross react with NCA but reacted only with CEA, providing evidence for a unique CEA determinant. Yet a third and most common type of antiserum to CEA reacted equally well with CEA and NCA and was unable to distinguish between the two. This third type of anti-CEA was completely absorbed with NCA. Failure to recognize this type of anti-CEA would lead to erroneous conclusions regarding the existence of a unique antigenic determinant on CEA.