Functions of uterine natural killer cells are mediated by interferon gamma production during murine pregnancy

The dominant lymphocytes in healthy human and murine implantation sites are pregnancy-associated uterine natural killer (uNK) cells. These cells produce 90% of pregnancy-induced, uterine interferon (IFN)-gamma, a cytokine that regulates expression of more than 0.5% of the mouse genome. Implantation sites in uNK cell-deficient and IFN-gamma -signal-disrupted mice display anomalies in decidua and its spiral arteries. Reconstruction of uNK cell-deficient females with bone marrow containing normal NK cell progenitors, establishes uNK cells and reverses the anomalies. Grafts from IFN-gamma (-/-) mice are restored uNK cells, but the uNK cells did not reverse the phenotypes. This review focusses on the functions of uNK cell-derived IFN-gamma and the genes that it may regulate in the pregnant uterus.