Extravillous trophoblast cells express the immunomodulatory HLA class Ib molecules HLA-G and HLA-F, interacting with receptors on maternal immune cells. These molecules were found on extravillous trophoblast cells. Endometrial biopsies taken from female patients undergoing in vitro fertilization (IVF) treatment at a reproductive clinic were used to create primary endometrial stromal cell (ESC) cultures (n=5). Prospective controlled cohort research was carried out, in which the participants consisted of 85 women with a previous experience with RIF and 36 control women who were beginning their first fertility therapy and had no previous experience with RIF. ESCs’ HLA protein expression was analyzed using flow cytometry and western blot techniques, respectively. Using immunohistochemistry and a digital image processing system, the specific immunological markers HLA-F and HLA-G, CD56 and CD16 (NK cells), CD163 (M2 macrophages), FOXP3 (regulatory T cells), and CD138 (plasma cells) were analyzed in endometrial biopsies as part of the cohort study. During implantation, the HLA-F protein was expressed in the endometrium. In addition, the levels of HLA-F protein differed depending on the HLA-F single-nucleotide polymorphisms (SNP) genotypes and diplotypes of the women, which were previously found to be connected with variances in the length of time it took for women to become pregnant. It was found that anti-inflammatory CD163+ M2 macrophage infiltration and CD56+ uNK cell abundance were positively linked with endometrial HLA-F for the entire cohort. On the other hand, this was not the case for CD56+ individuals in the RIF subgroup for female infertility. In the RIF subgroup with known cases of female infertility, the levels in the endometrial stroma were negatively correlated with plasma progesterone concentrations. Glandular sHLA-G expression was also found to positively correlate with the number of uNK cells in the RIF subgroup that did not have a diagnosis of female infertility. However, this correlation was negative in the RIF subgroup with a diagnosis of female infertility.
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