Carcinoembryonic antigen in fetal tissues and in material serum.

The occurrence of CEA was extensively adsorbed to eliminate cross-reactions with CEA-related antigens. After the first trimester of pregnancy CEA was found throughout the gastrointestinal tract by both techniques, whereas the other fetal tissues and fetal serum did not contain detectable amounts of CEA. The CEA-level of all 69 sera of pregnant women was below 2.5 ng/ml. The excretory nature of CEA was suggested by the localization of CEA in the luminal border of the alimentary tract and by the finding that the CEA concentration in the content of fetal gastrointestinal canal was higher than in the surrounding tissue. Gel filtration on Sepharose 4B showed that molecular weight of CEA immunoreactive material of the fetal gut was similar to that of CEA purified from colon cancer, but a minor component with a higher molecular weight was eluted in the void volume. When tested in radioimmunoassay, the CEA immunoreactive material in both peaks gave an inhibition curve parallel to that of purified CEA.