The influence of maternal immunoglobulin-G-antibodies on indirect haemagglutination in newborns.

High antibody titers against Escherichia coli were found in 100 randomly selected pregnant women by means of indirect haemagglutination (IHA). After birth, sera from the umbilical vein of the newborns were also tested. It was found that the indirect haemagglutination titers of the children were strongly influenced by the IgG which had been transferred via the placenta. Twenty-two sera of newborns showed an increased IHA-titer against E. coli, but only seven children displayed specific IgM antibodies, determined by indirect immunofluorescence. After chromatographic separation of the sera into IgG and IgM fractions, it was demonstrated that isolated antibodies of the IgG type alone can produce increased IHA titers. The assumption that the indirect haemagglutination is determined almost exclusively by antibodies of the IgG type is unfounded. Therefore, indirect haemagglutination is not suitable as a screening-test for newborns.