Effect of pregnancy uterine microenvironment on the expression of NKG2A,NKG2D and their ligands in decidual NK cells

AIM：To investigate the expression of NKG2A,NKG2D and their ligands in pregnancy uterine micro-environment and to probe the function of NKG2A and NKG2D imbalance expression during the immunotolerance at the fetal-maternal boundary.METHODS：Decidual lymphocytes and peripheral lymphocytes were obtained from 30 women during 6-9 weeks of pregnancy who were undergoing selective termination.FACS technology was used to detect NK cells number and NKG2A,NKG2D expression.RT-PCR was used to investigate HLA-E and MICA mRNA in trophoblast tissue.RESULTS：Natural killer cells predominate,accounting for 70% of pregnancy endometrial lymphocytes.FACS results indicated that NKG2A was significantly increased in decidual NK cells as compared with that in peripheral NK cells,accounting for 97.86%±1.75% and 33.35%±10.92%.The difference between them in NKG2A expression was significant (P<0.05).Although the levels of NKG2D in decidual NK cells were similar to that in peripheral NK cells,accounting for 93.21%±4.52% and 97.80%±1.72%,respectively,the difference between them in NKG2A expression was also significant (P<0.05).At the same time,we found HLA-E mRNA in the trophoblast tissue.There was no proof yet on the expression of NKG2D ligand-MICA on trophoblast.CONCLUSIONS：Natural killer cells are the predominant lymphocytes during the first trimester of decidual tissue.These cells have a great different antigenic phenotype with peripheral natural killer cells.Decidual natural killer cells have high expression of NKG2A and trophoblast tissue expressed HLA-E.This may be an important factor contributing to the immunotolerance at the fetal - maternal boundary during pregnancy.