Aberrant expression of intercellular adhesion molecule-1 and killer inhibitory receptors induces immune tolerance in women with pelvic endometriosis

OBJECTIVE: To investigate host immunologic response to endometriosis in terms of intercellular adhesion molecule (ICAM)-1 expression by macrophages and killer cell inhibitory receptor (KIR) expression by natural killer (NK) cells. DESIGN: Case-control study of immunologic markers. SETTING: University hospital. PATIENT(S): Twenty-eight Japanese women with endometriosis. Control subjects were 26 women without endometriosis. Diagnoses were made at laparoscopy. INTERVENTION(S): Venipuncture and laparoscopic peritoneal fluid collection. MAIN OUTCOME MEASURE(s): ICAM-1 expression by macrophages and KIR expression by NK cells, measured by flow cytometry. RESULT(S): In women with endometriosis, expression of ICAM-1 by peritoneal macrophages was significantly lower and expression of KIR by NK cells in peritoneal fluid and peripheral blood was significantly higher than in control subjects. CONCLUSION(S): Properties of macrophages and NK cells in women with endometriosis promote immunotolerance to implanted tissue in the peritoneal environment. Increased KIR(+)NK cells in peripheral blood may represent a risk factor for endometriosis.