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The regulation of uterine and peripheral blood natural killer (NK) cells has been associated with problems related to reproductive immunology such as recurrent pregnancy loss (RPL), implantation failure or preeclampsia. NKp46, one of the natural cytotoxicity receptors (NCRs), is a unique marker that functions in NK cell cytotoxicity and cytokine production. Expression of NKp46 on NK cells is lower in women with recurrent pregnancy loss and pregnancy-induced hypertension. Moreover, expression of NKp46 on peritoneal fluid NK cells is lower in women with pelvic endometriosis. Therefore, evaluation of NKp46 on peripheral blood NK cells may provide a means of screening for reproductive abnormalities. Recently, a new type of NK cell, the NK22 cell, has been reported. This cell may be a regulator not only of the mucosal barrier but also of reproduction.For women with RPL showing abnormal uterine and/or peripheral blood NK cells, both intravenous immunoglobulin treatment and intralipid treatment have been reported. The effects of these treatments are still controversial, and further studies are needed in order to clarify their true impact. The present review examines variations in the expression of NCRs on NK cells, the participation of NK22 cells in reproduction, and the possible use of intravenous immunoglobulin or intralipid treatment for women with recurrent pregnancy loss and NK cell abnormality. [ABSTRACT FROM AUTHOR]

Natural killer (NK) cells are innate lymphoid cells (ILCs) that participate to the clearance of pathogen-infected cells and tumour cells. NK cells and subsets of ILCs express the natural cytotoxicity receptors (NCRs) NKp46, NKp44 and NKp30 at their surface. NCRs have been shown to recognize a broad spectrum of ligands ranging from viral-, parasite- and bacterial-derived ligands to cellular ligands; however, the full identification of NCR ligands remains to be performed and will undoubtedly contribute to a better understanding of NK cell and ILC biology. [ABSTRACT FROM AUTHOR]

Problem To investigate the role of natural cytotoxicity receptor, NKp46 expression in cytokine-producing NK cells. Method of Study CD56+/ NKp46+ NK cells from the peripheral blood and the uterine endometrium were magnetically separated. IFN-γ, TNF-α, IL-4, IL-10, and TGF-β1 expressions on NK cells were investigated using multicolor flow cytometry. Results Peripheral blood and uterine endometrial NK cells were grouped into 4 subpopulations based upon the degree of CD56 and NKp46 expressions. NKp46 expression was associated with higher frequency of cytokine-producing NK cells, including CD56dim NK cells. The percentage of TNF-α+ and IL-10+ NK cells per total CD56+/ NKp46+ NK cells in the uterine endometrium showed a significant correlation with those of the peripheral blood in all subpopulations, but that of IFN-γ+, IL-4+, and TGF-β1+ NK cells showed partial correlation. Conclusion Expression of NKp46 is involved in cytokine production of CD56+ NK cells in the peripheral blood and the uterine endometrium. [ABSTRACT FROM AUTHOR]