Identification of syncytiotrophoblast-associated IgG in term human placentae

A mouse monoclonal antibody (H318) with specificity for an antigenic determinant in the C gamma 2 domain of human IgG, which was produced following immunisation with purified syncytiotrophoblast plasma membranes, has been shown to stain strongly human syncytiotrophoblast in immunofluorescence on cryostat section of term placental villous tissue. The staining was more pronounced with this antibody than with other monoclonal antibodies to the C gamma 2 domain of human IgG produced following the same immunisation or immunisation with isolated IgG. It appears that the H318 antibody may recognise an antigenic determinant which is enhanced on IgG that is associated with syncytiotrophoblast, possibly resultant from its interaction with IgG-binding structures.