Natural Killer Cells: Key Players in Endometriosis.

Endometriosis affects more than 10% of women, causing significant pain and morbidity. It is also a significant cause of infertility. The aetiology of the disease remains an enigma, and the mechanisms responsible for the associated infertility are unclear. A role for immune cells in endometriosis has been postulated, with attention directed towards natural killer (NK) cells and macrophages. NK cells kill tumours and infected cells but also have roles in tissue remodelling in several organs including the uterus and are key to successful pregnancy. Here, we explore evidence (from peer-reviewed published articles) of phenotypic and functional abnormalities in NK cell subpopulations of women with endometriosis. It is clear that peripheral blood NK cells and peritoneal NK cells have reduced cytotoxic function in women with endometriosis. Uterine NK cells have a vital role in infertility, but very little research has been carried out in this area. We propose that abnormal u NK cell activity may contribute to the pathogenesis of endometriosis and its associated infertility and that future research should focus on this complex area.