KIR2DL1 and endometriosis: Maeda et al. [9] studied the expression of NK inhibitory receptor CD158a+ in the peripheral blood of endometriosis subjects using flow cytometry and observed a statistically significant increase of 3.8% (17.5% ± 9.9% vs. 13.8% ± 7.7%, p = 0.009) in the endometriosis group compared with the control group.