In patients with endometriosis and pelvic pain syndrome, we observed a positive correlation of the percentage of CD4+CTLA-4+ T lymphocytes to the number of monocytes (R = 0.381, p = 0.013), and negative correlations of CD4+CTLA-4+ T lymphocytes to the percentage of CD3-CD16+CD56+ NK cells (R = −0.599, p < 0.001) and the percentage of CD3+CD16+CD56+ NKT-like cells (R = −0.364 p = 0.018). This evidence concerns the gene CTLA4 and endometriosis.