Endometriotic tissues produce immunosuppressive factors

In order to study the possible role of the immune functions in the pathogenesis of endometriosis, effects of supernatants from endometrial and endometriotic tissue cultures on the natural killer (NK) activity were examined by determining the lymphocyte cytotoxicity toward an erythroleukemic cell line (K562). Endometrial and endometriotic tissues were obtained at the time of operation from patients with ectopic endometriosis or uterine myoma. The normal peritoneum and myoma tissues were used as controls. The supernatants obtained by culturing the ectopic endometriotic tissues for 24-48 h had significant (p < 0.01) suppressive effects on NK activity of peripheral blood lymphocytes (PBL) from a healthy woman, compared to the supernatants from the normal peritoneum and the myoma tissues. There was no significant difference between NK activities of PBL from patients with ectopic endometriosis and age-matched healthy women. However, the NK activity in patients with low NK status before surgery was significantly elevated after surgery while that in patients with normal NK status before surgery was not changed. Although PBL from the same healthy women could significantly lyse the endometrial cells, the ability was about-one-third the level at which they could lyse K562 cells. These results suggest that the immunosuppressive factors secreted by endometriotic tissues may be involved in the local implantation and development of ectopic endometriosis.