Objective: We determined the effect of sera from patients who have endometriosis on natural killer cell activity.
Study design: The natural killer cell activity of lymphocytes from healthy volunteers was examined after incubation with sera from patients who had endometriosis or from controls, with K562 cells used as targets.
Results: Lymphocytes treated with sera from patients who had endometriosis expressed significantly lower levels of cytotoxicity compared with lymphocytes treated with control sera. This suppression of cytotoxicity was dose dependent, and the degree of suppression was proportional to the incubation time of the effector cells with the sera. Decreased cytotoxicity after serum treatment was also observed with sera from patients who had been treated with danazol.
Conclusions: These findings show that humoral factors that can inhibit natural killer cell activity in vitro are present in the peripheral blood of patients who have endometriosis; moreover, they suggest that the suppressed natural killer cell activity may allow the development of endometrial cells at ectopic sites.