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Alpha-feto-protein during development and in disease.

An alpha-feto-protein (AFP) is present in many mammals, in birds, and in sharks during development. The AFP present in different species have similar physicochemical properties and often have common antigenic determinants. Their study, both in health and disease, has provided a useful model for the understanding of other phase-specific antigens and the activation of the genes which control their synthesis. In the human fetus, the level of AFP falls with increasing maturity. The more sensitive methods of detection have disclosed that this fetal protein persists in trace amounts throughout life and its level increases in maternal blood during pregnancy. The principal sites of synthesis are the fetal liver and in some mammals, the yolk sac splanchnopleur. In humans as well as in mice and cows, it is notable that the synthesis of AFP is increased in liver cancer cells and that high levels of this protein are present in serum. Elevated values of AFP have also been detected in human subjects with undifferentiated tumours of the testis and ovary. A fall to normal levels has been noted in cases of complete remission after surgery and a return to high levels in patients who develop metastases. In some patients with hepatitis a temporary rise in the level of AFP has also been observed. In recent years, the detection of high levels of AFP in amniotic fluid has proved to be of great value for the prenatal diagnosis of neural-tube defects. Abnormal levels have also been found in the amniotic fluid or in maternal serum in cases of spontaneous abortion. Such measurements are now being assessed as a methodof monitoring abnormal pregnancy.