Pelvic endometriosis and natural killer cell immunity

Endometriosis is a chronic disease that commonly affects women in their reproductive age. It has been reported that the infertility due to endometriosis is largely caused by pelvic adhesion, oocyte damage, and so on. There are several causes of endometriosis including bacterial infections, immunological abnormalities, epigenetics, and aberrant DNA methylation. The natural killer (NK) cells present in the peritoneal fluid express CD16 and CD56. They also express NK cell inhibitory receptors and activating receptors and usually work to eliminate endometrial cells in the retrograde menstruation. However, in women with endometriosis, the changes in these receptors and production of cytokines by NK cells cause the onset and progression of endometriosis. In this review, we have focused on the role of NK cells in pelvic endometriosis and presented the immunological abnormalities in endometriosis including the possibility of future treatment.