Characterization of the phagocytic cells isolated from the human placenta.

The present study has shown that the human placenta (first trimester and full term) contains a significant population of mononuclear cells (isolated by proteolytic treatment) expressing receptors for Fc(IgG) and C3 and bearing surface immunoglobulin that is probably cytophilic. The cells, as assessed by morphology, resemble macrophages and actively partake in both immune and nonimmune phagocytosis. The receptor and phagocytic characteristics of the placenta suggest that it may be regarded as an important compartment of the reticuloendothelial system and that these properties probably contribute significantly to its defensive role in utero.