Phenotypically similar but functionally distinct NK cell populations within the human maternal-fetal interface [scRNA-seq]

Natural Killer cell function within tissues extends beyond exerting cytotoxicity, encompassing a range of functions that are just starting to become fully elucidated. In the context of human placentation, NK cells play a key role in enabling initial placentation, which is associated with the acquisition of tolerance-like properties. If and to which extent NK cells maintain these tolerance-like properties over the course of human pregnancy is still poorly understood. We have employed a single-cell sequencing approach using the BD RhapsodyTM system to study the transcriptomic profile of Natural Killer (NK) cells in the decidual-placental interface (DPI) and the decidua (in comparison to NK cells from the maternal circulating blood and the cord blood). We found that NK cells from both location had similar transcriptional profile with the presence of resident NK cells. Yet, when stimulated in vitro, CD103+CD69+ tissue-resident NK cells exhibited distinct effector function from one another. Together, our findings reveal the presence of distinct functional resident NK cell populations in two anatomically adjacent tissues at healthy full-term pregnancies.