Reduced frequency of perforin-positive CD8+ T cells in menstrual effluent of endometriosis patients compared to healthy controls

Background: Endometriosis is a widespread disease in women of reproductive age. The disease often reduces life quality of women affected by symptoms like dysmenorrhea, dyspareunia or infertility. Diagnosis remains challenging and no causal treatments exist until now. The scientific literature indicates many immunological changes like reduced cytotoxicity of natural killer cells and macrophages or altered concentrations of cytokines or cell adhesion molecules in women with endometriosis. Research has been concentrated on immunological alterations in peripheral blood, endometrial tissue and peritoneal fluid of women with endometriosis. Yet, knowledge on immunological differences in menstrual effluent is scarce. The aim of this study was to investigate menstrual effluent of hormone-free women with endometriosis in comparison to age matched healthy controls regarding selected immunological parameters. Methods: 12 women with endometriosis and 11 healthy controls were included in the study. Menstrual effluent (ME) was collected using menstrual cups over a time period of 24 h, and venous blood samples (PB) were taken. Mononuclear cells were obtained from ME (MMC) and PB (PBMC) using density gradient centrifugation and analyzed using flow cytometry. Furthermore, concentrations of cell adhesion molecules (ICAM-I and VCAM-I) and cytokines (IL-6, IL-8 and TNF-α) were measured in centrifugation supernatant of ME and plasma of PB. Results: The comparison of MMC from women with endometriosis and healthy controls revealed a significantly lower frequency of perforin-positive cells among CD8+ T cells in endometriosis patients compared to healthy controls. No additional differences regarding frequencies of CD8+ or CD4+ T cells, regulatory T cells (Tregs), NK cell subsets or monocytic subsets could be detected between MMC or PBMC, of endometriosis patients and healthy controls. Comparing MMC with PBMC revealed that MMC contained significantly more B cells and significantly less T cells than PBMC. Among the T cells, the CD4/CD8 ratio was significantly higher in MMC, and Tregs were significantly less common in MMC. T cells and NK cells expressed significantly more CD69 in MMC., NK cells of the MMC were predominantly CD56bright/CD16dim and the CD56dim NK cell subset had a low frequency of perforin+ cells, in contrast to CD56dim NK cells of PBMC, which were predominantly perforin-positive. However, NKp46 was significantly more expressed on NK cells from MMC. Finally, the endometriosis group had significantly lower plasma ICAM-I concentrations than the control group. There were no significant differences in VCAM-1, IL-6, IL-8 or TNF-α between the two groups. Conclusion: MMC are distinctively different from PBMC and, thus, seem to be of endometrial origin. The CD8+ T cells from the ME were significantly less perforin-positive in endometriosis patients than in healthy controls, suggesting a reduced cytotoxic potential.