Estrogen-regulated CD200 inhibits macrophage phagocytosis in endometriosis.

Endometriosis (EMS) is a benign disease that is related to estrogen, immune disorders and inflammation. The purpose of this research was to determine the expression of CD200 in EMS and to clarify its role in the pathogenesis of the disease. The levels of serum CD200 in patients with and without EMS were determined by ELISA. Furthermore, the expression of CD200 in normal eutopic endometrium and ectopic endometrium was detected by immunohistochemistry and western blotting. The CD200 receptor (CD200R) in macrophages in peritoneal fluid (pMØ) obtained from controls and patients with EMS was examined by western blotting. CD200 expression in human endometrial stromal cells (HESCs) stimulated with 17β-estradiol (E2) was measured by western blotting. Furthermore, macrophages were stimulated with different concentrations of CD200 and the effect on phagocytosis was analyzed. The plasma CD200 levels of patients with EMS was significantly increased compared with controls (P = 0.0173, 95%CI [18.75, 159.6]). Compared with normal eutopic endometrium, the expression of CD200 was significantly increased in ectopic endometrial tissues. The CD200R expression in pMØ obtained from patients with EMS was increased compared with the controls (P = 0.0244). CD200 expression in HESCs stimulated with E2 was up-regulated. As the levels of CD200 increased, macrophage phagocytosis in vitro gradually decreased. CD200 is an estrogen-induced molecule that impairs macrophage phagocytosis and may contribute to the immune escape of ectopic lesions in EMS.