Background: The mechanisms of the increase in the percentage of alpha-fetoproteins (AFPs) that strongly binds to Lens culinaris agglutinin (AFP-L3) in pregnancies with a trisomy 21 fetus have not been analyzed. To investigate the oligosaccharide variants of AFP produced by normal fetuses and fetuses with trisomy 21, the lectin reactivity of AFP was analyzed.
Methods: Fetal liver tissue, amniotic fluid, and maternal serum were obtained from five normal pregnancies and five pregnancies with a trisomy 21 fetus. The percentages of AFP reactive to lectins were determined by lectin-affinity electrophoresis coupled with antibody-affinity blotting.
Results: The percentages of AFP-L3 in the fetal liver and the maternal serum were 23.9 and 27.0%, respectively, in normal pregnancies, and 28.7 and 38.5%, respectively, in pregnancies with a trisomy 21 fetus. There was no statistically significant difference between the percentage in the fetal liver and the percentage in the maternal serum in normal pregnancies; however, a significant difference (P < 0.01) was found in pregnancies with a trisomy 21 fetus. In regard to the percentage of AFP-L3 in the fetal liver, there was no significant difference; however, a significant difference (P < 0.05) was found in the maternal serum between normal pregnancies and pregnancies with a trisomy 21 fetus.
Conclusions: The transference of the AFP-L3 fraction might be relatively high in the placentas of women carrying a trisomy 21 fetus, and this could be the one of the reasons for the increase in the percentage of AFP-L3 in the maternal serum in pregnancies with a trisomy 21 fetus.