Decreased expression of killer cell inhibitory receptors on natural killer cells in eutopic endometrium in women with adenomyosis

Background: Increased expression of killer cell inhibitory receptors (KIRs) has been found on natural killer (NK) cells in peritoneal fluid in women with endometriosis. In this study, we tried to measure the expression of KIRs on NK and T cells in women with adenomyosis, in an attempt to find the possible role of KIRs in the development of adenomyosis. Methods: A total of 10 women with adenomyosis (study group) and 12 women with uterine myoma (control group) were included in this study. The expression of KIRs, including NKB1, GL183, EB6 and CD94, on NK and T cells in myometrium and endometrium was examined by flow cytometry. Results: There was a decreased expression of NKB1 and GL183 on NK cells in the endometrium, but not in the myometrium, in women with adenomyosis. However, the expression of KIRs on T cells, either CD4⁺ or CD8⁺, was not different in either myometrium or endometrium between women with and without adenomyosis. Conclusions: The expression of KIRs on NK cells was decreased in eutopic endometrium in women with adenomyosis. It may be a compensatory effect in which the NK cytotoxicity is activated in order to eradicate the abnormal endometrial cells that might exit of the eutopic site of the endometrium.