To investigate the impact of P4 on the inflammatory responses in endometriosis, we first examined infiltration and activation of peritoneal macrophages in response to endometrial cells by IHC or IF analysis using antibodies against the pan-macrophage biomarker (F4/80), M1 (CCR7), or M2 (CD206), respectively [41]. This evidence concerns the gene CCR7 and endometriosis.