The Role of Macrophages in the Placenta

Placenta formation occurs through a complex and coordinated effort between the fetus’s extraembryonic tissues and the gravid endometrial tissues. Many macrophages are present in the placenta throughout pregnancy and have been detected as early as day 10 of pregnancy (Chang et al., 1993). Placental macrophages include Hofbauer cells of the fetal chorionic villi and decidual macrophages of the maternal decidua basalis (Figure 1) (Bulmer & Johnson, 1984). Functions of placental macrophages include the production of substances that regulate local immune reactions (such as factors that regulate maternal immunological tolerance and fetal protection) and that promote angiogenesis in the placenta during its development (Mues et al., 1989; Sevala et al., 2007). Although they represent a significant presence on both the maternal and fetal sides of the placenta, placental macrophage functions have not been completely elucidated and still remain a significantly studied area of investigation.