The partial characterisation of maternal anti-trophoblast antibody responses generated during normal human pregnancy.

The anti-trophoblast antibody response generated during a normal human pregnancy and detected by a recently developed enzyme-linked immunosorbent assay, was partially characterised in terms of maternal influences, nature of the antibodies and nature of the antigenic determinants present on the syncytiotrophoblast plasma membrane. The level and incidence of the response was significantly affected by maternal parity, while the maternal ABO, but not Rhesus, blood group antigens exerted a minor influence. The antibody response was predominantly mediated by IgG molecules of the IgG1,2 and 4 subclasses. The IgG molecules existed in the maternal sera either in the form of 'free' molecules or were involved in immune complexes. The antibodies interacted with determinants that were present on all the placental membranes tested and hence are possibly organ specific. The antigenic specificities were absent from erythrocytes and peripheral blood lymphocytes.