Alpha-fetoprotein (AFP) is a major plasma protein produced by the yolk sac and the liver during fetal life. It is expressed in fetal liver at varying levels throughout development and is present only in trace amounts in normal adult tissues. AFP can be detected at abnormally high concentrations in hepatocellular carcinomas as well as in the plasma and ascitic fluid of adults with hepatoma. The total AFP in serum was separated into three peaks (AFP-L1, AFP-L2 and AFP-L3) during the elution course.

The AFP-L2 was a part of total AFP.
The AFP-L2 fraction, which is known to be derived mostly from yolk sac tumor may be a sensitive indicator for a yolk sac tumor derived AFP, leading to an earlier detection of tumor recurrence during pregnancy.