Increased killer inhibitory receptor KIR2DL1 expression among natural killer cells in women with pelvic endometriosis

OBJECTIVE: To investigate the host immunologic response to endometriosis in terms of killer inhibitory receptor (KIR) expression by natural killer (NK) cells. DESIGN: Case-control study of immunologic markers. SETTING: University hospital. PATIENT(S): We compared cells from Japanese women with laparoscopically diagnosed endometriosis to cells from 40 women with other laparoscopic diagnoses. INTERVENTION(S): Peripheral venous blood sampling and laparoscopic peritoneal fluid collection. MAIN OUTCOME MEASURE(S): Flow cytometry was used to assess expression of KIR by NK cells in the cell samples. RESULT(S): The percentage of cells that expressed KIR2DL1 among NK (KIR2DL1(+)NK) cells in peritoneal fluid and peripheral blood was significantly higher in women with endometriosis than in controls. The proportion of KIR2DL1(+)NK cells in peripheral blood NK cells before and 1 month after laparoscopic surgery did not differ significantly. CONCLUSION(S): The proportion of KIR2DL1(+)NK cells was increased in peritoneal fluid and peripheral blood in women with endometriosis; this difference is probably related to NK cell suppression in endometriosis. This increase in KIR2DL1 expression by NK cells may represent a risk factor in the pathogenesis of endometriosis.