Recognition of trophoblast HLA class I molecules by decidual NK cell receptors - A review

During placentation the extravillous trophoblast (EVT) cells migrate throug h the decidua towards the maternal spiral arteries. The walls of the arteri es are then destroyed by trophoblast resulting in an increased blood flow t o the fetus. These EVT express HLA-G, HLA-E and HLA-C, an unusual combinati on of two non-classical and one classical MHC class I molecules. The decidu a is infiltrated by distinctive uterine natural killer (NK) cells during th e time of trophoblast invasion. These cells express a variety of receptors (CD94/NKG2, KIR and ILT) which are known to recognize HLA class I molecules . There is, therefore, a mechanism for molecular recognition of the placent al trophoblast cells. The possible functional consequences of this uterine NK cell-trophoblast interactions are uncertain. One possible result is in a n altered NK cell cytokine profile which modulates the invasive proclivity of the EVT. In this way placentation could be controlled. (C) 2000 IFPA and Harcourt Publishers Ltd.