Decreased natural killer cell activity in women with endometriosis.

Natural killer (NK) cell activity is characterized by the spontaneous capacity of lymphoid cells derived from nonimmunized hosts to recognize and lyse certain tumor cell lines, virus-infected cells and transplanted tumor cell lines. Endometriosis is characterized by implantation and proliferation of autologous ectopic tissue in the pelvic cavity. Therefore, we focused on examining NK cell activity in women with endometriosis. NK cell activity in peripheral blood from women with endometriosis was lower than in women without endometriosis. On the basis of this finding, we analyzed also the effect of peripheral sera of women with endometriosis on NK cell activity. In the presence of peripheral sera of women with endometriosis, NK cell activity was significantly suppressed as compared with the sera of women without endometriosis. The suppressive effect of sera of women with endometriosis on NK cell activity showed dose-dependent curves. These studies provide the speculation that natural immunity mediated by NK cells may modulate the development of endometrial implants.