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Endometriosis, affecting 10% of women, is defined as implantation, survival, and growth of endometrium-like/endometriotic tissue outside the uterine cavity, causing inflammation, infertility, pain, and susceptibility to ovarian cancer. Despite extensive studies, its etiology and pathogenesis are poorly understood and largely unknown. The prevailing view is that the immune system of endometriosis patients fails to clear ectopically disseminated endometrium from retrograde menstruation. Exosomes are small extracellular vesicles that exhibit immunomodulatory properties. We studied the role of endometriotic tissue-secreted exosomes in the pathophysiology of endometriosis. Two exosome-mediated mechanisms known to impair the immune response were investigated: 1) downregulation of NKG2D-mediated cytotoxicity and 2) FasL- and TRAIL-induced apoptosis of activated immune cells. We showed that secreted endometriotic exosomes isolated from supernatants of short-term explant cultures carry the NKG2D ligands MICA/B and ULBP1-3 and the proapoptotic molecules FasL and TRAIL on their surface, i.e., signature molecules of exosome-mediated immune suppression. Acting as decoys, these exosomes downregulate the NKG2D receptor, impair NKG2D-mediated cytotoxicity, and induce apoptosis of activated PBMCs and Jurkat cells through the FasL- and TRAIL pathway. The secreted endometriotic exosomes create an immunosuppressive gradient at the ectopic site, forming a "protective shield" around the endometriotic lesions. This gradient guards the endometriotic lesions against clearance by a cytotoxic attack and creates immunologic privilege by induction of apoptosis in activated immune cells. Taken together, our results provide a plausible, exosome-based mechanistic explanation for the immune dysfunction and the compromised immune surveillance in endometriosis and contribute novel insights into the pathogenesis of this enigmatic disease., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Problem: Tumors compromise the patients' immune system to promote their own survival. We have previously reported that HGSC exosomes play a central role, downregulating NKG2D cytotoxicity. Primary surgery's effect on tumor exosomes and NKG2D cytotoxicity in HGSC patients has not been studied before. The overall objective of this study was to explore the effect of surgery on the exosome-induced impairment of NKG2D cytotoxicity in HGSC., Method of Study: Paired pre- and post-operative blood samples were subjected to cell and exosome analyses regarding the NKG2D receptor and ligands, and NKG2D-mediated cytotoxicity. Lymphocytes were phenotyped by immunoflow cytometry. Exosomes, isolated by ultracentrifugation, and characterized by nanoparticle tracking analysis, transmission and immune electron microscopy and western blot were used in functional cytotoxic experiments. HGSC explant culture-derived exosomes, previously studied by us, were used for comparison., Results: HGSC exosomes from patients' sera downregulated NKG2D-mediated cytotoxicity in NK cells of healthy donors. In a subgroup of subjects, NKG2D expression on CTLs and NK cells was upregulated after surgery, correlating to a decrease in the concentration of exosomes in postoperative sera. An overall significantly improved NKG2D-mediated cytotoxic response of the HGSC patients' own NK cells in postoperative compared to preoperative samples was noted., Conclusions: Surgical removal of the primary tumor has a beneficial effect, relieving the exosome-mediated suppression of NKG2D cytotoxicity in HGSC patients, thus boostering their ability to combat cancer., (© 2022 The Authors. American Journal of Reproductive Immunology published by John Wiley & Sons Ltd.)