Microheterogeneity forms of alpha-fetoprotein present in amniotic fluid.

The microheterogeneity forms of human alpha-fetoprotein present in amniotic fluid were studied in affinity immunoelectrophoresis using two lectins: concanavalin A and Lens culinaris agglutinin. Ninety-seven samples of amniotic fluid collected throughout gestation were obtained from pregnancies in which there was no fetal malformation. Two samples of amniotic fluid from pregnancies complicated by anencephaly and one sample obtained from an empty gestational sac were also studied. The changes in relative concentrations of AFP microheterogeneity forms during gestation are described. It is suggested that concanavalin A is suitable for the demonstration of malformations of the central nervous system in the first and second trimester of pregnancy while in the third trimester it would be of no value. The results of this study suggest that Lens culinaris agglutinin might be suitable for this purpose in the third trimester of gestation, but this needs to be confirmed in a larger study. The optimal concentrations of both lectins were investigated. In addition, a simple method of rocket affinity electrophoresis is also described. The possible mechanisms responsible for the changes in relative concentrations of microheterogeneity forms of alpha-fetoprotein during gestation and in pathological conditions are discussed.