Expression of inhibitory-motif killer immunoglobulin-like receptor, KIR2DL1, is increased in natural killer cells from women with pelvic endometriosis

PROBLEM: We investigated inhibitory and activation motif expression of killer immunoglobulin-like receptor (KIR) by natural killer (NK) cells, which may be pathogenetically involved in endometriosis. METHOD OF STUDY: We compared cells from 24 Japanese women laparoscopically diagnosed with endometriosis, to cells from 25 women with other laparoscopic diagnoses. KIR expression by NK cells was assessed in peripheral blood (PB) and peritoneal fluid (PF) by flow cytometry. Intracellular immunoreceptor tyrosine-based (IT) inhibitory and activation motifs (ITIM and ITAM) of KIR in PB was assessed by Western blotting. RESULTS: ITIM-KIR expression by PB NK cells was significantly and similarly greater than ITAM-KIR expression in women with and without endometriosis. Percentages of CD56(+) NK cells in PB and PF did not differ significantly between women with and without endometriosis; however, the percentage of CD158a(+) cells among CD56(+) NK cells in PB and PF was significantly higher in women with than without endometriosis. CONCLUSIONS: ITIM-KIR expressing NK cells might confer tolerance to peritoneal endometriotic implants.