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 method of monitoring abnormal pregnancy. 