HUMAN UTERINE NK CELLS HAVE A SIMILAR REPERTOIRE OF KILLER INHIBITORYAND ACTIVATORY RECEPTORS TO THOSE FOUND IN BLOOD, AS DEMONSTRATED BY RT-PCR AND SEQUENCING

The expression of natural killer (NK) cell receptors specific for HLA class I molecules has been studied in CD56(bright), CD3(-) NK cells is olated from the pregnant uterine mucosa, the decidua. RT-PCR was perfo rmed on cDNA from uterine NK cells with primers designed to amplify me mbers of the killer inhibitory receptor (KIR)/killer activatory recept or (KAR) gene family. Sequencing of the PCR products revealed that ute rine NK cells express KIR/KAR which have two or three extracellular im munoglobulin superfamily (Ig-SF) domains. NK receptors for both groups of HLA-C alleles were found. KIR, characterised by a long cytoplasmic tail containing the immune receptor tyrosine-based inhibitory motif ( ITIM), and KAR, characterised by a short cytoplasmic domain with a tra nsmembrane region containing a char ed lysine, were both identified. D ifferent individuals appear to have a distinct but overlapping reperto ire of KIR/KAR. No new members of this NK receptor gene family were id entified in the uterine CD56(bright) NK cells. Similar findings were o btained from non-pregnant endometrial tissues representative of differ ent stages of the menstrual cycle. Immunohistology confirmed that the KIR protein products were expressed by decidual NK cells. These result s reveal that NK receptors for trophoblast HLA class I molecules are p resent in maternal uterine NK cells. Fetal trophoblast cells infiltrat ing the decidua express HLA-G and HLA-C gene products. This suggests t hat maternal recognition of the fetus may be mediated by an NK allorec ognition system. (C) 1997 Elsevier Science Ltd.