MACROPHAGE POPULATIONS IN THE HUMAN-PLACENTA AND AMNIOCHORION

Abstract

Fetal and maternal macrophage populations in human utero-placental tissues at different stages of gestation were studied using immunohistological and histochemical techniques. A large population of macrophages was identified within maternal decidualized endometrium in term and 1st trimester tissues, although lymphoid cells also constitute a major component of the bone marrow-derived cells in the decidua of early pregnancy. In contrast, fetal macrophages contributed nearly all of the substantial bone marrow-derived cell population within placental chorionic villous mesenchyme and within the mesenchyme of the term amniochorion. Apart from a small population of stellate intensely HLA-DR positive cells in term placental villous stroma, these extra-embryonic fetal macrophages consistently expressed both the leu-M3 tissue macrophage antigen and lysosomal enzyme activities. The major HLA-DR positive cell population of fetal amniochorion apparently comprises ''classical'' macrophages rather than dendritic type cells. These various macrophage populations may perform vital phagocytic and degradative functions within utero-placental tissues and amniochorion.