The unique properties of human NK cells in the uterine mucosa.

Natural killer (NK) cells are lymphocytes of the innate immune system that are able to kill hazardous pathogens and tumours. It was recently recognized that NK cells also possess non-destructive functions. NK cells were shown to interact with T, B, DC cells and macrophages and consequently shape the adaptive immune response. In addition, activated NK cells were shown to be quite efficient antigen-presenting cells. Here we review the unique properties of human NK cells in the uterine mucosa prior to and during pregnancy. We discuss the role of decidual NK cells and suggest that their major function is to assist in fetal development. Further we discuss the function and origin of endometrial NK cells and define some questions that need to be addressed in future research.