Multiple FC receptors in the human placenta.

The presence of Fc receptors on endothelium and trophoblastic tissue in cryostat sections of full-term human placentae has been verified. Fc receptor activity on stem vessel endothelium can be manifest both by immunofluoresence with heat-aggregated IgG and by haemadsorption with antibody-sensitized erythrocytes. However, Fc receptor activity on trophoblastic tissue is manifest only in the haemadsorption reaction, and not in the immunofluorescence reaction. The haemadsorption and immunofluorescence were both independent of temperature, and were completely abolished by formaldehyde fixation of the tissue sections. Both reactions were expressed on first-trimester placental tissue, although more limited and diffuse. In terms of their anatomical location and specificity characteristics the Fc receptors in human placentae may have a biological significance.