Increase in the expression of killer cell inhibitory receptors on peritoneal natural killer cells in women with endometriosis

Objective: Malfunction of peritoneal natural killer cells (NK) may result i n endometriosis. The present study was designed to determine whether the de crease in NK cytotoxicity occurs at early and advanced stages of endometrio sis and is due to the increase in the NK inhibition receptors. Design: A case control study. Setting: A tertiary-care infertility center. Patient(s): A total of 44 women (controls, n = 11; women with early-stage e ndometriosis, n = 11; and women with advanced-stage endometriosis, n = 22) were included in this study. Intervention(s): Laparoscopic examination. Main Outcome Measure(s): NK cytotoxicity was determined by assay of Cr-51 r elease against K562 cells, and the expression of killer cell inhibitory rec eptors (KIR, including NKB1, GL183, and EB6) in NK cells was examined by fl ow cytometry. Result(s): Women with endometriosis showed a decrease in peritoneal NK cyto toxicities against K562 at early and advanced stages of endometriosis. The expression of KIR (NKB1 and EB6) was significantly elevated in the peritone al NK cells of women with advanced-stage endometriosis compared with contro ls. KIR (NKB1) was also significantly increased in peritoneal NK cells of w omen with advanced-stage endometriosis, compared with those of women with e arly-stage endometriosis. Conclusion(s): The results of this study suggest that the decrease in perit oneal NK cytotoxicities against K562 is observed and that this disease may be partially due to the increased expression of KIR on these NK cells. (Fer til Steril(R) 2000;74:1187-91. (C) 2000 by American Society for Reproductiv e Medicine).