From a mother's perspective, a fetus is a bag full of foreign antigens—invaders against which an immune system might be expected to protect. But, according to Jacob Hanna, Ofer Mandelboim (Hebrew University, Jerusalem, Israel), and colleagues, certain immune cells actually help fetal cells to invade the uterus and ensure an adequate blood supply. Their success is essential to avoid the often fatal condition of preeclampsia.
All this cellular action takes place in the decidua, the outer lining of the uterus during pregnancy. Up to 40% of the cells in this tissue are maternal natural killer (NK) cells—but specifically the NK cells rich in CD56. Unlike the majority of circulating NK cells, these dNK cells are good at excreting proinflammatory cytokines and bad at killing infected cells.
The Israeli group found that dNK cells produce chemokines that can attract embryonic cells called trophoblasts. These trophoblasts form...
