Distribution of tumor-associated antigen CEA and cross-reacting NCA in fetal organs.

The organ distribution of the tumor-associated carcinoembryonic antigen (CEA), and that of the normal tissue component NCA (non-specific cross-reacting antigen) have been investigated in the fetus. Organ extracts from five fetuses between 14 and 21 weeks of age were analysed by radioimmunoassay using specific antisera. CEA was detected in large amounts (800--1,650 ng/g) in fetal colon and in barely detectable amounts in lung and placental tissue. This differed from NCA, which could be detected in almost all organ extracts analysed. The highest concentration of NCA was measured in fetal colon and the content increased with the gestational age of the fetus. High amounts of NCA were also found in the liver, spleen and placental tissue. The gel elution profiles of CEA and NCA from an amniotic fluid pool and a pool of colonic extracts were also determined. CEA eluted similarly to the marker 125I--CEA purified from liver metastasis of colonic carcinoma. The NCA-reactive material was found in three distinct peaks.