Direct and Indirect endocrine-mediated suppression of human endometrial CD8+T cell cytotoxicity

Regulation of endometrial (EM) CD8+T cells is essential for successful reproduction and protection against pathogens. Suppression of CD8+T cells is necessary for a tolerogenic environment that promotes implantation and pregnancy. However, the mechanisms regulating this process remain unclear. Sex hormones are known to control immune responses directly on immune cells and indirectly through the tissue environment. When the actions of estradiol (E₂), progesterone (P) and TGFβ on EM CD8+T cells were evaluated, cytotoxic activity, perforin and granzymes were directly suppressed by E₂ and TGFβ but not P. Moreover, incubation of polarized EM epithelial cells with P, but not E₂, increased TGFβ secretion. These findings suggest that E₂ acts directly on CD8+T cell to suppress cytotoxic activity while P acts indirectly through induction of TGFβ production. Understanding the mechanisms involved in regulating endometrial CD8+T cells is essential for optimizing reproductive success and developing protective strategies against genital infections and gynecological cancers.