Cellular immune environment in endometrial polyps

Study objective To investigate the immune environment of endometrial polyps (EPs). Design Prospective case-control study. Setting Teaching hospital and university research laboratory. Patient(s) Reproductive-age women undergoing hysteroscopy dilation and curettage for benign indications. Samples were collected from women with (n = 23) and without (n = 40) EPs. Intervention(s) Endometrial samples were immunohistochemically stained with antibodies against mast cells (MCs) and regulatory T cells (Tregs). Main outcome measure(s) Tryptase+, chymase+, and c-Kit+ MCs and Foxp3+ Tregs were quantified in EPs and polyp-adjacent, polyp-distant, and control endometrium. Result(s) Densities of all MC types were highly significantly increased in EPs compared with adjacent, distant, and control endometrium. Chymase+ and c-Kit+ MCs were increased in density in adjacent compared with control endometrium. c-Kit+ MCs were also increased in distant compared with control endometrium. Foxp3+ Treg density was increased in EPs compared with distant and control endometrium and decreased in distant compared with control endometrium. Conclusion(s) This study provides novel insights into localized disturbances in the cellular immune environment within EPs consistent with EPs being inflammatory lesions associated with MC overactivity. Tregs are likely to be recruited to EPs in an attempt to suppress the inflammatory process due to the greatly increased presence of MCs. These immunologic disturbances are likely to be involved in the causation of abnormal bleeding and infertility in premenopausal women with EPs, and their role in the pathophysiology requires further research.