Enhanced CD56 Expression and Increased Number of CD56 ^+bright Cells in the Peripheral Blood of Untreated Endometriosis Patients

The significantly increased proportion of peripheral CD56^+brightNK/eNK cells may result from migration of these cells from ectopic endometrial tissue. The downregulation of NKG2D receptor expression in PBMCs may be mediated by immunosuppressive endometriotic exosomes, as previously reported by us. Taken together, our results suggest that: (1) the impaired NK cell cytotoxicity in untreated endometriosis patients may be due both to an influx of CD56^+bright/eNK cells and exosome-induced NKG2D receptor downregulation; and (2) elevated numbers of peripheral CD56^+bright NK cells could be considered as a potential diagnostic marker for endometriosis.