1. A review of the literature has shown that the major soluble antigens in amniotic
fluid at term are of serum type, and that of these antigens albumin, transferrin and
group-specific component are mainly of maternal origin. It was not clear whether this
conclusion applied to the protein in amniotic fluid earlier in gestation, nor had
extensive studies been made into the nature of the non-serum protein in amniotic fluid.
The object of the work presented in this thesis was to investigate the nature and origin
of the soluble protein in amniotic fluid throughout pregnancy.2. An immunological investigation showed that when rabbits were immunised with amniotic
fluid, the majority of their immune response was directed against serum protein. The
major antigens in the fluid were found to include albumin, -antitrypsin, group-specific
component, and transferrin.3. A method was developed for phenotyping group-specific component (Gc) in amniotic
fluid and in serum by antibody-antigen crossed electrophoresis. Maternal serum and
amniotic fluid was collected from each of 56 pregnancies at between ten and thirty-eight
weeks of gestation, and in each case the Gc phenotype of the fluid was the same as the
maternal phenotype. In 11 of these cases, a sample of fetal serum was also obtained,
and in four cases in which the fetus was discordant from the mother, the Gc phenotype
of the fluid was the same as the maternal phenotype. From this it was concluded that
the majority of the Gc in amniotic fluid was of maternal origin, from ten weeks of
pregnancy onwards.4. The concentrations of albumin, a.-antitrypsin, Gc, and transferrin were measured in
amniotic fluid and in maternal and fetal serum. The concentration patterns of the four
proteins in amniotic fluid were very similar and maximal concentrations were found between
twenty and thirty weeks, showing a general similarity to the total protein concentration.
When the concentrations of the individual proteins in amniotic fluid were expressed as
ratios of the concentrations in maternal or fetal serum, a general similarity was found
between the ratios of albumin, -antitrypsin, Gc, and transferrin. These concentration
ratios were much less than that found for a-fetoprotein. From this it was concluded
that the albumin, -antitrypsin, and transferrin in amniotic fluid were mainly of
maternal origin from about ten weeks of gestation onwards
