Immunological studies on the nature and origin of the major proteins in amniotic fluid.

Abstract

SummaryThe nature of soluble proteins in human amniotic fluid has been investigated by immunizing rabbits with concentrated amniotic fluid obtained from patients at various stages of pregnancy. The resulting antisera showed that in all cases the majority of the immune response to amniotic fluid was directed against proteins of serum origin, with albumin, α1‐antitrypsin, group‐specific component and transferrin being quantitatively most important. During gestation the concentration changes of these proteins were found to be similar to those of the total soluble protein. The maternal serum: amniotic fluid concentration ratios for albumin, α1‐antitrypsin and transferrin were similar to that found for group‐specific component (known to be of maternal origin), whilst the fetal serum: amniotic fluid concentration ratios for these four proteins were considerably less than that found for α‐fetoprotein (of fetal origin). From this and other data it is concluded that from ten weeks of gestation onwards the major soluble protein in amniotic fluid is primarily of maternal serum origin.