Based on the research outcomes about the role of ICs in the tumor microenvironment or autoimmunological diseases, we hypothesize that the PD-1/PD-L1/PD-L2 pathway may play a significant role in the implantation and growth of endometrial tissue in the peritoneal cavity, and may be related to the local immunosuppression in patients suffering from EMS. Here, PDCD1LG2 is linked to neoplasm.