NK22 Cells in the Uterine Mid-Secretory Endometrium and Peripheral Blood of Women with Recurrent Pregnancy Loss and Unexplained Infertility

ProblemWe aimed to investigate natural killer 22 (NK22) cells in the peripheral blood and the uterine endometrium of women with unexplained recurrent pregnancy loss (URPL) and unexplained infertility (UI). Method of studyPeripheral blood and endometrial samples were collected from women with URPL (n=43) and UI (n=38). Intracellular cytokine production, such as IL-22, IFN- and TNF-, and the expression of NKp46 on NK cells were analyzed by three-color flow cytometry. ResultsThe percentages of endometrial CD56(+)/IL-22(+) and CD56(dim)/IL-22(+) cells in women with URPL were significantly higher than those of UI (P<0.05, respectively). In addition, the percentage of CD56(bright)/IL-22(+) cells in women with RPL was negatively correlated with those of CD56(bright)/IFN-(+) and CD56(bright)/TNF-(+) in both peripheral blood and endometrial NK cells. This was not seen in women with UI. The percentage of CD56(bright)/IL-22(+) cells was negatively correlated with CD56(bright)/NKp46 expressing NK cells in peripheral blood. ConclusionEndometrial NK22 cells are differently regulated in women with URPL and UI. Women with URPL have higher level of NK22 cells with a potential to induce NK2 shift than women with UI.