ICAM1 and endometriosis: In patients with endometriosis, elevated expression of ICAM-1 on the human endometrial stromal cells gives rise to the shedding of soluble ICAM-1 (sICAM-1) from the cell surface into the peritoneal cavity, where sICAM-1 binds to the cell membranes of NK cells and interferes with their cytotoxic function, consequently hampering NK cell-mediated removal of ectopic endometrial cells in the peritoneal cavity, and can lead to the development of endometriosis.