The in vitro production of alpha--fetoprotein variants by human fetal organs.

We have demonstrated the immunological identity of alpha-fetoprotein (AFP) produced in vitro by various fetal organs such as the yolk sac, liver, intestine and kidney. AFP produced in vitro by these organs, present in fetal serum and in samples of amniotic fluid was, however, heterogeneous when studied by lectin affinity immunoelectrophoresis. Results obtained with Concanavalin A were comparable to those obtained with Lentil agglutinin, but Concanavalin A separated AFP into two variants only, while Lentil agglutinin recognised three AFP variants. AFP produced by the yolk sac, intestine and kidney was similar in their proportions of variants and differed clearly from liver AFP. The ratios of AFP variants present in fetal serum were dissimilar to those of yolk sac AFP and of liver AFP. Relative amounts of AFP variants in fetal serum were similar in the first and last trimester of gestation. The proportions of AFP variants present in amniotic fluid in the first trimester of gestation were different from fetal serum, but, at the end of pregnancy, they become identical to those observed in fetal serum. Application of AFP variants for prenatal and cancer diagnosis is discussed.