From Infection to Pregnancy Complications: Key Role of the Immune Response of Placental Cells.

The infection of pregnant animals and women by , an intracellular bacterium, compromises both maternal health and foetal development. The placenta is targeted by as demonstrated by bacteriological and histological evidence. It now appears that placental strains of   are highly virulent compared to reference strains and that placental injury involves different types of placental cells. Trophoblasts, the major placental cells, are largely infected by C. and may represent a replicating niche for the bacteria. The placenta also contains numerous immune cells, including macrophages, dendritic cells, and mast cells. Placental macrophages are infected and activated by in an unusual way of M1 polarisation associated with bacterial elimination. Placental mast cells eliminate bacteria through a mechanism including the release of extracellular actin filaments and antimicrobial peptides. In contrast, impairs the maturation of decidual dendritic cells, favouring bacterial pathogenicity. Our aim is to review infections of human placentas, paying special attention to both the action and function of the different cell types, immune cells, and trophoblasts targeted by in relation to foetal injury.