Maternal immune cell investigation from intervillous blood of placentas with chronic histiocytic intervillositis: Directions for future research.

Chronic histiocytic intervillositis (CHI) is associated with adverse pregnancy outcome and results in placental inflammation characterized by maternal myeloid cells within the intervillous space. This intervillous space is part of the maternal-fetal interface, which provides a unique microenvironment for the immunologic crosstalk between intervillous blood and placental components. The pathophysiologic pathways of CHI are still unclear. Here, we conduct a narrative review on the current knowledge about CHI, intervillous blood sampling methods, and immune cell characteristics in the intervillous space of healthy term pregnancy. We highlight that the detailed phenotype and functional investigation of maternal immune cells from intervillous blood of placentas with CHI is expected to provide better understanding of the etiology of disease.