A search for antibodies in term maternal sera to solubilized syncytiotrophoblast surface components. A passive haemagglutination assay yields negative evidence

Using a passive haemagglutination assay, agglutinins against trophoblast components were detected in term maternal sera at titres above those of non-pregnant control sera. These agglutinin titres were independent of the family relationship between individual sera and trophoblast samples. They were unaffected by adsorption with excess packed fetal or paternal red blood cells or paternal lymphocytes. The agglutinins of both normal control and term maternal sera were found to elute in the macroglobulin fraction of serum having a molecular weight of greater than 350 kDa and were shown to be a component of euglobulin precipitates. The titres of the agglutinins were unaffected by adsorption using solid phase antibodies against human IgM and IgG from the sera. It was concluded that these agglutinins were not a maternal antibody response against trophoblast surface components.