This increase was even more pronounced in stage III/IV endometriosis (KIR2DL1+ 24.2% ± 16.1% vs. 12.3% ± 6.9%, p = 0.007 [8], 17.5% ± 8.7% vs. 11.7% ± 5.5%, p = 0.008 [7], CD158a+ 17.0% ± 12.3% vs. 12.3% ± 7.1%, p = 0.017 [9]) Matsuoka et al. [10] corroborated these findings, also reporting an increased percentage of CD158a+ in CD56+ NK cells in the peritoneal fluid of the endometriosis group (13.9% ± 7.5% vs. 7.6% ± 3.0%, p = 0.028). The gene discussed is KIR2DL1; the disease is endometriosis.