An increase of Treg cells in the peripheral blood is associated with a better in vitro fertilization treatment outcome

Androgen receptor modulates Foxp3 expression in CD4+CD25+Foxp3+ regulatory T-cells

CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells are able to inhibit proliferation and cytokine production in effector T-cells and play a major role in immune responses and prevention of autoimmune disease. A master regulator of Treg cell development and function is the transcription factor Foxp3. Several cytokines, such as TGF-β and IL-2, are known to regulate Foxp3 expression as well as methylation of the Foxp3 locus. We demonstrated previously that testosterone treatment induces a strong increase in the Treg cell population both in vivo and in vitro. Therefore we sought to investigate the direct effect of androgens on expression and regulation of Foxp3. We show a significant androgen-dependent increase of Foxp3 expression in human T-cells from women in the ovulatory phase of the menstrual cycle but not from men and identify a functional androgen response element within the Foxp3 locus. Binding of androgen receptor leads to changes in the acetylation status of histone H4, whereas methylation of defined CpG regions in the Foxp3 gene is unaffected. Our results provide novel evidence for a modulatory role of androgens in the differentiation of Treg cells.

T regulatory markers expression in unexplained recurrent spontaneous abortion

OBJECTIVE

To evaluate expression of glucocorticoid-induced tumor necrosis factor receptor (GITR), cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and IL-10 in peripheral blood mononuclear cells (PBMCs) of 20 women with unexplained recurrent spontaneous abortion (URSA) compared to 20 normal non-pregnant women (NNP) during luteal phase in the window of implantation.

METHODS

Quantitative real-time PCR (qRT-PCR) was performed using the Taqman method for expression of GITR and SYBR Green method for expression of CTLA-4 and IL-10.

RESULTS

Expression of CTLA-4 in the NNPs (median; interquartile range; 3; 1.8-10) was significantly higher than the URSAs (0.72; 0.26-3.81, p = 0.015). Expression of GITR in the NNPs (53; 10-139) was significantly higher than the URSAs (6; 3-27, p = 0.005). However, IL-10 expression in the URSAs was significantly higher than the NNPs, did not meet a significant value. A significant correlation was found between CTLA-4 and GITR expression in the study population (p = 0.0001).

CONCLUSIONS

Expression of CTLA-4 and GITR were significantly down-regulated in the URSAs compared to NNPs at the window of implantation, which shows the essential role of Treg cells in creating an immunological privileged site for fetus as an allograft at the maternal-fetal interface by high expression levels of CTLA-4 and GITR during a normal pregnancy.

Colonization of the upper genital tract by vaginal bacterial species in nonpregnant women

OBJECTIVE

The objective of the study was to evaluate the upper genital tract (UGT) presence of vaginal bacterial species using sensitive molecular methods capable of detecting fastidious bacterial vaginosis (BV)-associated bacteria.

STUDY DESIGN

Vaginal swabs were collected prior to hysterectomy. The excised uterus was sterilely opened and swabs collected from the endometrium and upper endocervix. DNA was tested in 11 quantitative polymerase chain reaction (PCR) assays for 12 bacterial species: Lactobacillus iners, L crispatus, L jensenii, Gardnerella vaginalis, Atopobium vaginae, Megasphaera spp, Prevotella spp, Leptotrichia/Sneathia, BVAB1, BVAB2, BVAB3, and a broad-range16S ribosomal ribonucleic acid gene assay. Endometrial fluid was tested with Luminex and an enzyme-linked immunosorbent assay for cytokines and defensins and tissue for gene expression of defensins and cathelicidin.

RESULTS

We enrolled 58 women: mean aged 43±7 years, mostly white (n=46; 79%) and BV negative (n=43; 74%). By species-specific quantitative PCR, 55 (95%) had UGT colonization with at least 1 species (n=52) or were positive by 16S PCR (n=3). The most common species were L iners (45% UGT, 61% vagina), Prevotella spp (33% UGT, 76% vagina) and L crispatus (33% UGT, 56% vagina). Median quantities of bacteria in the UGT were lower than vaginal levels by 2-4 log10 ribosomal ribonucleic acid gene copies per swab. There were no differences in the endometrial inflammatory markers between women with no bacteria, Lactobacillus only, or any BV-associated species in the UGT.

CONCLUSION

Our data suggest that the endometrial cavity is not sterile in most women undergoing hysterectomy and that the presence of low levels of bacteria in the uterus is not associated with significant inflammation.

Intrauterine insemination of cultured peripheral blood mononuclear cells prior to embryo transfer improves clinical outcome for patients with repeated implantation failures

Implantation failure is a major limiting factor in assisted reproduction improvement. Dysfunction of embryo–maternal immuno-tolerance pathways may be responsible for repeated implantation failures. This fact is supported by immunotropic theory stipulating that maternal immune cells, essentially uterine CD56+ natural killer cells, are determinants of implantation success. In order to test this hypothesis, we applied endometrium immuno-modulation prior to fresh embryo transfer for patients with repeated implantation failures. Peripheral blood mononuclear cells were isolated from repeated implantation failure patients undergoing assisted reproductive technology cycles. On the day of ovulation induction, cells were isolated and then cultured for 3 days and transferred into the endometrium cavity prior to fresh embryo transfer. This immunotherapy was performed on 27 patients with repeated implantation failures and compared with another 27 patients who served as controls. Implantation and clinical pregnancy were increased significantly in the peripheral blood mononuclear cell test versus control (21.54, 44.44 vs. 8.62, 14.81%). This finding suggests a clear role for endometrium immuno-modulation and the inflammation process in implantation success. Our study showed the feasibility of intrauterine administration of autologous peripheral blood mononuclear cells as an effective therapy to improve clinical outcomes for patients with repeated implantation failures and who are undergoing in vitro fertilization cycles.

The Paternal Contribution to Fetal Tolerance

Recognition of foreign paternal antigens expressed in the semi-allogeneic fetus by maternal immune cells is a requirement for successful pregnancy. However, despite intensive research activity during the last decades, the precise mechanisms contributing to the acceptance of the paternal alloantigens are still puzzling and pregnancy remains a fascinating phenomenon. Moreover, most studies focused on the maternal and fetal contribution to pregnancy success, and relatively little is known about the paternal involvement. In the current review, we address the contribution of paternal-derived factors to fetal-tolerance induction. First, we discuss data suggesting that in both humans and mice, the female body gets prepared for a pregnancy in every cycle, also in regard to male alloantigens delivered at coitus. Then, we provide an overview about factors present in seminal fluid and how these factors influence immune responses in the female reproductive tract. We further discuss ways of paternal alloantigen presentation and identify the immune modulatory properties of seminal fluid-derived factors with a special focus on Treg biology. Finally, we highlight the therapeutic potential of seminal fluid in different clinical applications.

Endocrine factors modulating immune responses in pregnancy

How the semi-allogeneic fetus is tolerated by the maternal immune system remains a fascinating phenomenon. Despite extensive research activity in this field, the mechanisms underlying fetal tolerance are still not well understood. However, there are growing evidences that immune–immune interactions as well as immune–endocrine interactions build up a complex network of immune regulation that ensures fetal survival within the maternal uterus. In the present review, we aim to summarize emerging research data from our and other laboratories on immune modulating properties of pregnancy hormones with a special focus on progesterone, estradiol, and human chorionic gonadotropin. These pregnancy hormones are critically involved in the successful establishment, maintenance, and termination of pregnancy. They suppress detrimental maternal alloresponses while promoting tolerance pathways. This includes the reduction of the antigen-presenting capacity of dendritic cells (DCs), monocytes, and macrophages as well as the blockage of natural killer cells, T and B cells. Pregnancy hormones also support the proliferation of pregnancy supporting uterine killer cells, retain tolerogenic DCs, and efficiently induce regulatory T (Treg) cells. Furthermore, they are involved in the recruitment of mast cells and Treg cells into the fetal–maternal interface contributing to a local accumulation of pregnancy-protective cells. These findings highlight the importance of endocrine factors for the tolerance induction during pregnancy and encourage further research in the field.

Regulatory T cells: regulators of life

Pregnancy still represents one of the most fascinating paradoxical phenomena in science. Immediately after conception, the maternal immune system is challenged by the presence of foreign paternal antigens in the semen. This triggers mechanisms of recognition and tolerance that all together allow the embryo to implant and later the fetus to develop. Tolerance mechanisms to maintain pregnancy are of special interest as they defy the classical immunology rules. Several cell types, soluble factors, and immune regulatory molecules have been proposed to contribute to fetal tolerance. Within these, regulatory T cells (Treg) are one of the most studied immune cell populations lately. They are reportedly involved in fetal acceptance. Here, we summarize several aspects of Treg biology in normal and pathologic pregnancies focusing on Treg frequencies, subtypes, antigen specificity, and activity as well as on factors influencing Treg generation, recruitment, and function. This review also highlights the contribution of fetal Treg in tolerance induction and addresses the role of Treg in autoimmune diseases and infections during gestation. Finally, the potential of Treg as a predictive marker for the success of assisted reproductive techniques and for therapeutic interventions is discussed.

Seminal fluid and the generation of regulatory T cells for embryo implantation

T regulatory (Treg) cells are essential mediators of the maternal immune adaptation necessary for embryo implantation. In mice, insufficient Treg cell activity results in implantation failure, or constrains placental function and fetal growth. In women, Treg cell deficiency is linked with unexplained infertility, miscarriage, and pre-eclampsia. To devise strategies to improve Treg cell function, it is essential to define the origin of the Treg cells in gestational tissues, and the regulators that control their functional competence and recruitment. Male seminal fluid is a potent source of the Treg cell-inducing agents TGFβ and prostaglandin E, and coitus is one key factor involved in expanding the pool of inducible Treg cells that react with paternal alloantigens shared by conceptus tissues. In mice, coitus initiates a sequence of events whereby female dendritic cells cross-present seminal fluid antigens and activate T cells, which in turn circulate via the blood to be sequestered into the endometrium. Similar events may occur in the human genital tract, where seminal fluid induces immune cell changes that appear competent to prime Treg cells. Improved understanding of how seminal fluid influences Treg cells in women should ultimately assist in the development of new therapies for immune-mediated pathologies of pregnancy.

Adaptive immune responses during pregnancy

It has long been believed that there is no immune interaction between mother and conceptus during pregnancy. This concept changed after evidence was provided that the maternal immune system is aware of the semiallogeneic conceptus and develops strategies to tolerate it. Since then, finely regulated mechanisms of active tolerance toward the fetus have been described. This Special Issue of the American Journal of Reproductive Immunology deals with these mechanisms. It begins with the description of minor histocompatibility antigens in the placenta; it further goes through adaptive immune responses toward paternal fetal antigens, mostly concentrating on regulatory T cells and molecules modulating the Th1/Th2 balance. The participation of antibody-producing B cells in normal and pathological pregnancies is also discussed. This introductory chapter resumes the concepts presented throughout the Issue and discusses the clinical applications raised from these concepts.

Regulatory T cells are baby's best friends

Regulatory T cells (Treg) are one of the most and best studied immune cell population during human and murine pregnancy, and there is a general consent about their expansion during pregnancy. However, the identification of new and more reliable Treg markers during the last years resulted in some controversies about the kinetics of various Treg subsets at different pregnancy stages. No doubt exists regarding the importance of Treg for a normal pregnancy as pregnancy complications like spontaneous abortion and preeclampsia could be associated with a reduced Treg number and activity. In future, more attention should be paid to bring established data from the bench to the bedside to force the development of adequate therapies for treatment of pregnancy complications. In this article, we summarize previous and recent data on several aspects of Treg biology during human and murine pregnancy.

The multi-differentiation potential of peripheral blood mononuclear cells

Peripheral blood is a large accessible source of adult stem cells for both basic research and clinical applications. Peripheral blood mononuclear cells (PBMCs) have been reported to contain a multitude of distinct multipotent progenitor cell populations and possess the potential to differentiate into blood cells, endothelial cells, hepatocytes, cardiomyogenic cells, smooth muscle cells, osteoblasts, osteoclasts, epithelial cells, neural cells, or myofibroblasts under appropriate conditions. Furthermore, transplantation of these PBMC-derived cells can regenerate tissues and restore function after injury. This mini-review summarizes the multi-differentiation potential of PBMCs reported in the past years, discusses the possible mechanisms for this multi-differentiation potential, and describes recent techniques for efficient PBMC isolation and purification.