Characterization of natural killer cells in nonobese diabetic/severely compromised immunodeficient mice during pregnancy

ObjectiveTo characterize uterine natural killer (uNK) cells in nonobese diabetic/severely compromised immunodeficient (NOD/SCID) mice and investigate the potential role of these cells in pregnancy tolerance.DesignAn animal model–based study.SettingAcademic research center in a university.Animal(s)Syngeneic pregnant NOD/SCID mice were compared with non-immunodeficient BALB/c mice.Intervention(s)Induction of Toll-like receptor (TLR) agonists.Main Outcome Measure(s)Flow cytometric analysis was performed to detect the percentage of cell subsets, and standard 51Cr release assay was performed to determine cytotoxicity.Result(s)The dominant subset of uNK cells in NOD/SCID mice is DX5 (CD49b)+, asialo ganglio-N-tetraosylceramide+, CD25+, CD122+, Thy-1 (CD90)hi, c-kit (CD117)hi, and interleukin-10+. In addition, the percentage of interferon-γ+ subset was slightly increased in response to selected TLR agonists in the NOD/SCID mice, whereas the corresponding percentage in BALB/c mice could be increased dramatically. Such an effect could be abrogated by inhibitors, including LY294002, SP600125, and PD98059. The significant increase of interferon-γ+ NK cell percentage in BALB/c mice was concomitant with the increase of the embryo resorption rate. In contrast, the resorption rate in NOD/SCID mice was not significantly increased upon the induction of polyinosinic polycytidylic acid or lipopolysaccharide. As expected, the NK cells from NOD/SCID mice display a detectable but lower cytotoxicity than BALB/c, as determined by standard 51Cr release assay. In addition, the uNK cells from NOD/SCID mice also display a hyposensitivity to lipopolysaccharide-induced production of inducible nitric oxide synthase.Conclusion(s)A considerable percentage of immature NK cells were detected at the fetomaternal interface in NOD/SCID mice. These cells were hyposensitive to the stimulation of selected TLR agonists. Such a status seemed to be beneficial for the maintenance of pregnancy.