Decidual CD4 Research Articles

Decidual CD8+T cells exhibit both residency and tolerance signatures modulated by decidual stromal cells

BackgroundDuring early pregnancy, tolerance of the semi-allogeneic fetus necessitates comprehensive modifications of the maternal immune system. How decidual CD8+T (CD8+dT) cells balance maternal tolerance of the fetus with defense from invading pathogens remains undefined.MethodsWe investigated the distribution patterns of CD8+T cells and their heterogeneity in paired peripheral blood and decidual tissue in the first trimester of pregnancy using flow cytometry and mRNA-Seq. Gene Set Enrichment Analysis was utilized to determine the transcriptional features of CD8+dT cells. Moreover, we examined activation of T cells when they were cocultured with trophoblasts, in addition to the effect of the fetal–maternal environment on peripheral CD8+T (CD8+pT) cells.ResultsWe found that, compared with CD8+pT cells, CD8+dT cells consisted mainly of effector memory cells (TEM) and terminally differentiated effector memory cells (TEMRA). Both TEM and TEMRA subsets contained increased numbers of CD27+CD28− cells, which have been shown to possess only partial effector functions. In-depth analysis of the gene-expression profiles of CD8+dT cells revealed significant enrichment in T cell exhaustion-related genes and core tissue residency signature genes that have been found recently to be shared by tissue resident memory cells and tumor−infiltrating lymphocytes (TILs). In accordance with gene expression, protein levels of the exhaustion-related molecules PD-1 and CD39 and the tissue resident molecules CD103 and CXCR3 were increased significantly with almost no perforin secretion in CD8+dT cells compared with CD8+pT cells. However, the levels of granzyme B, IFN-γ, and IL-4 in CD8+dT cells were increased significantly compared with those in CD8+pT cells. Both CD8+dT and CD8+pT cells were not activated after being cocultured with autologous trophoblast cells. Moreover, the production of granzyme B in CD103+CD8+dT cells decreased significantly compared with that in their CD103− counterparts. Coculture with decidual stromal cells and trophoblasts upregulated CD103 expression significantly in CD8+pT cells.ConclusionsOur findings indicate that the selective silencing of effector functions of resident CD8+dT cells may favor maternal–fetal tolerance and that the decidual microenvironment plays an important role in promoting the residency of CD8+T cells and their tolerance–defense balance.

Tissue-resident CD8+ T memory cells with unique properties are present in human decidua during early pregnancy.

Resident memory T (TRM ) cells reside in the uterus during pregnancy may play an important role in balancing maternal-fetal tolerance with anti-infectious immunity. Although CD8+ TRM and decidual CD8+ T cells have been extensively characterized, the properties of decidual CD8+ TRM (dTRM ) cells remain poorly defined. We investigated the heterogeneity, phenotypes, and functions of dTRM cells, and compared the proportion of dTRM cells between normal pregnancy and recurrent spontaneous abortion (RSA) using flow cytometry. Moreover, we cocultured peripheral CD8+ T (CD8+ pT) cells with trophoblast, or decidual stomal cells (DSCs) in the presence or absence of anti-TGF-β antibody or TGF-β type I receptor inhibitor to explore the effects of maternal-fetal environment on decidual CD8+ TRM cell formation. We found that CD69+ CD103+ TRM cells were abundant in CD8+ dT cells but not in CD4+ dT cells with effector-memory (EM, CD45RA- CCR7- ) phenotypes. The percentage of dTRM cells from RSA patients was significantly higher than that from normal pregnancy. Furthermore, dTRM cells showed increased expressions of chemokine receptors, T-cell exhaustion-related molecules, and produced more anti-inflammatorycytokines and effectorcytokines upon stimulation. Moreover, DSCs produced a considerable level of TGF-β and upregulated CD103 expression on CD69+ CD8+ pT cells, which can be significantly reversed by blocking TGF-β receptor. Our findings demonstrate that TRM cells with unique properties are present in the decidua during human early pregnancy. They possess an enhanced capacity to produce effector cytokines and regulatory molecules, which might be important in the balance between maternal-fetal immune tolerance and the capacity to aggressively respond to infections.

Mifepristone (RU486) Inducing Abortion in a Mouse Model by Regulating Innate and Adaptive Immune Responses

Objective: Mifepristone (RU486), one of the most common medications for artificial abortion, attenuates the immunoregulatory effects of progesterone. However, the specific immune regulatory mechanism of RU486 in abortion remains unknown. We intended to investigate the immunomodulatory effects of RU486 on abortion. Methods: Sixty female mice were divided into the control group (0 mg RU486) and RU486 group (2 mg/kg RU486). The uterus, peripheral blood, and spleen were obtained for isolation of specific cell types. The population and phenotype of immune cells in the decidua, peripheral blood, and spleen were analyzed using flow cytometry. Statistical differences between groups were determined using two-tailed t- test. For all statistical tests, P < 0.05 was considered statistically significant. Results: RU486 effectively induced abortion in pregnant mice, with a significantly higher number of decidual macrophages (dMφ) (control group = 25.55% ± 2.467%, RU486 group = 19.41% ± 1.423%; P < 0.05), especially the major histocompatibility complex IIhigh subset. No difference in Mφ number was observed in the spleen or peripheral blood. Moreover, the dMφ from mice with RU486-induced abortion displayed a remarkable activated phenotype, with increased expressions of inducible nitric oxide synthase, tumor necrosis factor-α, and interleukin (IL)-12 but decreased expressions of arginase-1 and IL-10. We also found elevated levels of decidual CD4+ T-cells in the RU486 group that exhibited a higher level of the proinflammatory cytokine interferon-γ and a lower level of the anti-inflammatory cytokines, IL-4 and IL-10. Conclusions: We report a new mechanism of RU486-induced abortion via the regulation of innate cell Mφ activation and the adaptive response of CD4+ T-cells present in the decidua but not the periphery.

The phenotype of decidual CD56+ lymphocytes is influenced by secreted factors from decidual stromal cells but not macrophages in the first trimester of pregnancy

During the first trimester of pregnancy the decidua is comprised of decidual stromal cells (DSC), invading fetal trophoblast cells and maternal leukocytes, including decidual natural killer (dNK) cells and macrophages. dNK cells are distinct from peripheral blood NK cells and have a role in regulating trophoblast invasion and spiral artery remodelling. The unique phenotype of dNK cells results from the decidual environment in which they reside, however the interaction and influence of other cells in the decidua on dNK phenotype is unknown. We isolated first trimester DSC and decidual macrophages and investigated the effect that DSC and decidual macrophage secreted factors have on CD56+ decidual lymphocyte receptor expression and cytokine secretion (including dNK cells). We report that DSC secreted factors induce the secretion of the cytokines IL-8 and IL-6 from first trimester CD56+ cells. However, neither DSC nor decidual macrophage secreted factors changed CD56+ cell receptor expression. These results suggest that secreted factors from DSC influence CD56+ decidual lymphocytes during the first trimester of pregnancy and therefore may play a role in regulating the unique phenotype and function of dNK cells during placentation.

The appropriate frequency and function of decidual Tim-3+CTLA-4+CD8+ T cells are important in maintaining normal pregnancy

Maternal decidual CD8+ T (dCD8+ T) cells must integrate the antithetical demands of maternal–fetal tolerance and anti-viral immunity to establish a successful pregnancy. T-cell immunoglobulin mucin-3 (Tim-3) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) are two important co-inhibitory molecules that regulating CD8+ T cells responses during infection and tumor. In the present study, we examined the co-expression of Tim-3 and CTLA-4 on CD8+ T cells during pregnancy and found the higher frequency of Tim-3+CTLA-4+dCD8+ T cells in response to trophoblasts. This Tim-3+CTLA-4+dCD8+ T cells subset showed an active status and produced more anti-inflammatory cytokines. Furthermore, the decreased number and altered function of Tim-3+CTLA-4+dCD8+ T cells correlated to miscarriage. Combined blocking Tim-3 and CTLA-4 pathways were highly effective in inhibiting the production of anti-inflammatory cytokines and were detrimental to the maintenance of pregnancy. Together, these findings supported that Tim-3 and CTLA-4 pathways might play positive roles in the establishment and/or maintenance of maternal–fetal tolerance so to promote the maintenance of normal pregnancy. So the reproductive safety must be considered, especially when anti-Tim-3/CTLA-4 antibody (and other immune checkpoint inhibitors) are used in pregnancy.

P19: Blockade of CTLA‐4 and Tim‐3 pathways induces fetal loss with altered cytokine profiles by decidual CD4+ T cells

American Journal of Reproductive ImmunologyVolume 81, Issue S1 p. 47-47 ABSTRACTS P19: Blockade of CTLA-4 and Tim-3 pathways induces fetal loss with altered cytokine profiles by decidual CD4+ T cells First published: 31 May 2019 https://doi.org/10.1111/aji.18_13120Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume81, IssueS1Special Issue: The 39th Annual Meeting of the American Society for Reproductive Immunology, 12-15 June 2019, Grand Rapids, Michigan, USAMay 2019Pages 47-47 RelatedInformation

P20: Tim‐3 and CTLA‐4 pathways help to regulate decidual CD8+ T cells function and maintain normal pregnancy

P20: Tim‐3 and CTLA‐4 pathways help to regulate decidual CD8⁺ T cells function and maintain normal pregnancy

Three Types of Functional Regulatory T Cells Control T Cell Responses at the Human Maternal-Fetal Interface

During pregnancy, maternal regulatory Tcells (Tregs) are important in establishing immune tolerance to invading fetal extravillous trophoblasts (EVTs). CD25HIFOXP3+ Tregs are found at high levels in decidual tissues and have been shown to suppress fetus-specific and nonspecific responses. However, limited data are available on additional decidual Treg types and the mechanisms by which they are induced. This study investigated three distinct decidual CD4+ Treg types in healthy pregnancies with a regulatory phenotype and the ability to suppress Tcell responses: CD25HIFOXP3+, PD1HIIL-10+, and TIGIT+FOXP3dim. Moreover, co-culture of HLA-G+ EVTs or decidual macrophages with blood CD4+ Tcells directly increased the proportions ofCD25HIFOXP3+ Tregs compared to Tcells cultured alone. EVTs also increased PD1HI Tregs that could be inhibited by HLA-C and CD3 antibodies, suggesting an antigen-specific induction. The presence of distinct Treg types may allow forthe modulation of a variety of inflammatory responses in the placenta.

The importance of the PD-1/PD-L1 pathway at the maternal-fetal interface

BackgroundOur goal with this study was to investigate the contribution of PD-1/PD-L1 immune-checkpoint pathway to maternal immunotolerance mechanisms.MethodsThirteen healthy pregnant women and 10 non-pregnant controls were involved in this project. PBMCs and DICs were isolated from peripheral blood and from decidual tissues. After the characterization of different immune cell subsets, we used fluorochrome-conjugated monoclonal antibodies to measure the expression level of PD-1, PD-L1, NKG2D, and CD107a molecules by flow cytometry.ResultsWe measured significant alternations in the proportion of decidual immune cell subsets compared to the periphery. Elevated PD-1 expression by decidual CD8+ T, CD4+ T, and NKT-like cells were also detected accompanied by the increased PD-L1 expression by decidual CD4+ T, Treg, NKT-like and CD56 + NK cell subsets compared to peripheral blood. The cytotoxic potential was significantly higher in PD-1- decidual immune cells compared to the periphery, however we measured a significantly lower cytotoxicity in the decidual PD-1+ CD8+ T cells compared with the peripheral subsets. An activation receptor NKG2D expression was decreased by the PD-1+ CD8+ T subsets in the first trimester compared to non-pregnant condition but the expression level of the decidual counterparts was significantly elevated compared to the periphery. The cytotoxic potential of decidual PD1/NKG2D double positive CD8+ T cells was significantly decreased compared to the peripheral subsets.ConclusionsBased on our results we assume that PD-1/PD-L1 pathway might have a novel role in the maintaining of the local immunological environment. Accompanied by NKG2D activating receptor this checkpoint interaction could regulate decidual CD8 Tc cell subsets and may contribute maternal immunotolerance.

Decidual Interleukin-22-Producing CD4+ T Cells (Th17/Th0/IL-22+ and Th17/Th2/IL-22+, Th2/IL-22+, Th0/IL-22+), Which Also Produce IL-4, Are Involved in the Success of Pregnancy.

Trophoblast expressing paternal HLA-C resembles a semiallograft, and could be rejected by maternal T cells. IL-22 seems to be involved in allograft rejection and thus could be responsible for miscarriages. We examined the role of decidual IL-22-producing CD4+ T on human pregnancy. In those experiencing successful pregnancy and those experiencing unexplained recurrent abortion (URA), the levels of IL-22 produced by decidual CD4+ T cells are higher than those of peripheral blood T cells. We found a correlation of IL-22 and IL-4 produced by decidual CD4+ T cells in those experiencing successful pregnancy, not in those experiencing URA. The correlation of IL-22 and IL-4 was also found in the serum of successful pregnancy. A prevalence of CD4+ T cells producing IL-22 and IL-4 (Th17/Th2/IL-22+, Th17/Th0/IL-22+, Th17/Th2/IL-22+, and Th0/IL-22+ cells) was observed in decidua of those experiencing successful pregnancy, whereas Th17/Th1/IL-22+ cells, which do not produce IL-4, are prevalent in those experiencing URA. Th17/Th2/IL-22+ and Th17/Th0/IL-22+ cells are exclusively present at the embryo implantation site where IL-4, GATA-3, IL-17A, ROR-C, IL-22, and AHR mRNA are expressed. T-bet and IFN-γ mRNA are found away from the implantation site. There is no pathogenic role of IL-22 when IL-4 is also produced by decidual CD4+ cells. Th17/Th2/IL-22+ and Th17/Th0/IL-22+ cells seem to be crucial for embryo implantation.

Blockade of CTLA-4 and Tim-3 pathways induces fetal loss with altered cytokine profiles by decidual CD4+T cells

The single and/or combination use of immune checkpoint blockade therapies in human infectious diseases and cancer are rapidly expanding. Despite early efforts, substantial uncertainty remains about the safety and efficacy of immune checkpoint blockade in some populations. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and T-cell immunoglobulin mucin-3 (Tim-3) are the major targetable co-inhibitory receptors on T cells. Here we showed that in animal studies, treatment with either CTLA-4- or Tim-3-blocking antibody caused greater susceptibility to fetal loss with altered cytokine profiles by decidual CD4+T (dCD4+T) cells. CTLA-4 and Tim-3 pathways appeared to play key roles in maintaining maternal-fetal tolerance by regulating the function of dCD4+T cells. In addition, the abnormality in number and functionality of dCTLA-4+Tim-3+CD4+T cells was associated with miscarriage. These findings underscored the important roles of the CTLA-4 and Tim-3 pathways in regulating dCD4+T cells function and maintaining normal pregnancy. Our study also emphasized the importance of careful consideration of reproductive safety when choosing immune checkpoint blockade therapies in real world clinical care.

P9: Transcriptional and alternative splicing signatures for decidual CD8+ T cells during human early pregnancy

American Journal of Reproductive ImmunologyVolume 80, Issue S1 p. 63-63 ABSTRACTS P9: Transcriptional and alternative splicing signatures for decidual CD8+ T cells during human early pregnancy First published: 26 June 2018 https://doi.org/10.1111/aji.08_12984Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume80, IssueS1Special Issue: American-Sino Joint Meeting of Reproductive Immunology (ASRI-CSI 2018), June 28-1 July, 2018 Shanghai, ChinaJune 2018Pages 63-63 RelatedInformation

Deep Surveying of the Transcriptional and Alternative Splicing Signatures for Decidual CD8+ T Cells at the First Trimester of Human Healthy Pregnancy.

Decidual CD8+ (dCD8) T cells have been proposed to play important roles in immune protection against the invading pathogens and in tolerance toward the growing semi-allogeneic fetus during early pregnancy. However, their phenotypic and functional characteristics remain poorly defined. Here, we performed the first analysis of the transcriptional and alternative splicing (AS) signatures for human first-trimester dCD8 T cells using high-throughput mRNA sequencing. Our data revealed that dCD8 T cells have distinct transcriptional and AS landscapes when compared with their autologous peripheral blood CD8+ (pCD8) T counterparts. Furthermore, human dCD8 T cells were observed to contain CD8-Treg and effector-memory T-cell subsets, and display enhanced functionality in terms of degranulation and cytokine production on a per-cell basis. Additionally, we have identified the novel splice junctions that use a high ratio of the non-canonical splicing motif GC-AG and found that AS is not a major contributor to the gene expression-level changes between paired pCD8 and dCD8 T cells. Together, our findings not only provide a comprehensive framework of the transcriptional and AS landscapes but also reveal the functional feature of human dCD8 T cells, which are of great importance in understanding the biology of these cells and the physiology of human healthy pregnancy.

Mixed signature of activation and dysfunction allows human decidual CD8+ T cells to provide both tolerance and immunity

Understanding how decidual CD8+ T cell (CD8+ dT) cytotoxicity is regulated and how these cells integrate the competing needs for maternal-fetal tolerance and immunity to infection is an important research and clinical goal. Gene-expression analysis of effector-memory CD8+ dT demonstrated a mixed transcriptional signature of T cell dysfunction, activation, and effector function. High protein expression of coinhibitory molecules PD1, CTLA4, and LAG3, accompanied by low expression of cytolytic molecules suggests that the decidual microenvironment reduces CD8+ dT effector responses to maintain tolerance to fetal antigens. However, CD8+ dT degranulated, proliferated, and produced IFN-γ, TNF-α, perforin, and granzymes upon in vitro stimulation, demonstrating that CD8+ dT are not permanently suppressed and retain the capacity to respond to proinflammatory events, such as infections. The balance between transient dysfunction of CD8+ dT that are permissive of placental and fetal development, and reversal of this dysfunctional state, is crucial in understanding the etiology of pregnancy complications and prevention of congenital infections.

IL-25 promotes Th2 bias by upregulating IL-4 and IL-10 expression of decidual γδT cells in early pregnancy.

Decidual immune cells (DICs), consisting of both innate and adaptive immune cells, have a pivotal role in maintaining immune tolerance for normal pregnancy. Our previous study demonstrated that interleukin (IL)-25 stimulates the proliferation of decidual stromal cells (DSCs) in an autocrine manner. However, the role of IL-25 in functional regulation of DICs is largely unknown. Flow cytometry was used to analyze the expression of IL-25 and its receptor (IL-17RB) in DICs, and the effect of IL-25 on the expression of Ki-67, IL-4, IL-10, interferon (IFN)-γ and transforming growth factor (TGF)-β in decidual γδT cells. In addition, ELISA assays were performed to detect the secretion of IL-10 and TGF-β in decidual γδT cells. The present findings indicated that decidual CD56 bright CD16-natural killer (NK) cells, natural killer T (NKT) cells, regulatory T (Treg) cells, CD3+ T cells, macrophages and γδT cells co-expressed IL-25 and IL-17RB, particularly γδT cells. Recombinant human (rh) IL-25 protein upregulated the expression of Ki-67, IL-4, and IL-10, but downregulated the expression of IFN-γ in γδT cells; however, anti-human IL-25 or IL-17RB neutralizing antibody reversed these effects. These data suggest that IL-25 may promote IL-10 production by γδT cells as well as the proliferation of γδT cells, and possibly forms a positive feedback loop to maintain a T helper 2 cell bias at the maternal-fetal interface and further contributes to the maintenance of successful pregnancy.

Decidual T Cells Exhibit a Highly Differentiated Phenotype and Demonstrate Potential Fetal Specificity and a Strong Transcriptional Response to IFN.

Immune tolerance during human pregnancy is maintained by a range of modifications to the local and systemic maternal immune system. Lymphoid infiltration is seen at the implantation site of the fetal-maternal interface, and decidual NK cells have been demonstrated to facilitate extravillous trophoblast invasion into maternal decidua during the first trimester, optimizing hemochorial placentation. However, although there is considerable T cell infiltration of the maternal decidua, the functional properties of this T cell response remain poorly defined. We investigated the specificity and regulation of CD4+ and CD8+ T cells obtained from human third trimester decidua and demonstrated that decidual CD4+ and CD8+ T cells exhibit a highly differentiated effector memory phenotype in comparison with peripheral blood and display increased production of IFN-γ and IL-4. Moreover, decidual T cells proliferated in response to fetal tissue, and depletion of T regulatory cells led to an increase in fetal-specific proliferation. HY-specific T cells were detectable in the decidua of women with male pregnancies and were shown to be highly differentiated. Transcriptional analysis of decidual T cells revealed a unique gene profile characterized by elevated expression of proteins associated with the response to IFN signaling. These data have considerable importance both for the study of healthy placentation and for the investigation of the potential importance of fetal-specific alloreactive immune responses within disorders of pregnancy.

Interleukin-17-producing decidual CD4+ T cells are not deleterious for human pregnancy when they also produce Interleukin-4

Background Trophoblast expressing paternal HLA-C antigens resemble a semiallograft, and could be rejected by maternal CD4+ T lymphocytes. We examined the possible role in human pregnancy of Th17 cells, known to be involved in allograft rejection and reported for this reason to be responsible for miscarriages. We also studied Th17/Th1 and Th17/Th2 cells never investigated before. We defined for the first time the role of different Th17 subpopulations at the embryo implantation site and the role of HLA-G5, produced by the trophoblast/embryo, on Th17 cell differentiation.

An investigation of the relationship between recurrent spontaneous abortion and memory T follicular helper cells.

Immune tolerance with respect to a semi-allogeneic fetus plays a key role in the establishment of a pregnancy. Memory T follicular helper (Tfh) cells have a central role in the regulation of the adaptive immune response. Much of our knowledge of memory Tfh cells' function comes from immune-related diseases. However, the true physiological characteristics of memory Tfh cells and their mode of action in pregnancy remain unclear. Deciduas and blood were obtained from 25 recurrent spontaneous abortion (RSA) patients undergoing surgical abortion and 19 normal women in early pregnancy undergoing elective termination. RSA patients were grouped into antibody-positive patients and antibody-negative patients, respectively. The memory Tfh cells with the CD4+ CXCR5+ PD1+ CCR7- and CD4+ CXCR5+ PD-1+ ICOS+ phenotypes were assessed by flow cytometry. The B cells were evaluated by flow cytometry. A correlation analysis of the subsets of memory Tfh cells and B cells in antibody-positive RSA patients was made by the Pearson test. Memory Tfh cells with the CD4+ CXCR5+ PD1+ CCR7- and CD4+ CXCR5+ PD-1+ ICOS+ phenotypes showed a significant increase in RSA patients compared to women with a normal pregnancy who had chosen termination. When RSA patients were grouped according positive or negative antibodies, it was surprising to find that decidual CD4+ CXCR5+ PD-1+ ICOS+ memory Tfh cells significantly increased in RSA patients with positive antibody compared to RSA patients with negative antibody. However, the percentages of CD4+ CXCR5+ PD1+ CCR7- memory Tfh cells did not change in the deciduas of the two groups. Circulating and decidual B cells significantly increased in antibody-positive RSA patients compared with antibody-negative RSA patients. Correlation analysis indicated a strong association between the decidual CD4+ CXCR5+ PD-1+ ICOS+ memory Tfh cells and B cells in antibody-positive RSA patients. These new findings provide unique insights into memory Tfh cells in mediating feto-maternal immune tolerance.

Distinct Transcriptional and Alternative Splicing Signatures of Decidual CD4+ T Cells in Early Human Pregnancy.

Decidual CD4+ T (dCD4 T) cells are crucial for the maternal-fetal immune tolerance required for a healthy pregnancy outcome. However, their molecular and functional characteristics are not well elucidated. In this study, we performed the first analysis of transcriptional and alternative splicing (AS) landscapes for paired decidual and peripheral blood CD4+ T (pCD4 T) cells in human early pregnancy using high throughput mRNA sequencing. Our data showed that dCD4 T cells are endowed with a unique transcriptional signature when compared to pCD4 T cells: dCD4 T cells upregulate 1,695 genes enriched in immune system process whereas downregulate 1,011 genes mainly related to mRNA catabolic process and the ribosome. Moreover, dCD4 T cells were observed to be at M phase, and show increased activation, proliferation, and cytokine production, as well as display an effector-memory phenotype and a heterogenous nature containing Th1, Th17, and Treg cell subsets. However, dCD4 T cells undergo a comparable number of upregulated and downregulated AS events, both of which are enriched in the genes related to cellular metabolic process. And the changes at the AS event level do not reflect measurable differences at the gene expression level in dCD4 T cells. Collectively, our findings provide a comprehensive portrait of the unique transcriptional signature and AS profile of CD4+ T cells in human decidua and help us gain more understanding of the functional characteristic of these cells during early pregnancy.

Cytotoxic potential of decidual NK cells and CD8+ T cells awakened by infections

To establish a healthy pregnancy the maternal immune system must tolerate fetal allo-antigens, yet remain competent to respond to infections. The ability of decidual NK cells (dNK) to promote migration of fetal extravillous trophoblasts (EVT) and placental growth as well as the capacity of EVT to promote immune tolerance are topics of high interest and extensive research. However, the problem of how dNK and decidual CD8+ T cells (CD8+ dT) provide immunity to infections of the placenta and the mechanisms that regulate their cytolytic function has thus far largely been ignored. Fetal EVT are the most invasive cells of the placenta and directly interact with maternal decidual immune cells at this maternal-fetal interface. Besides the expression of non-polymorphic HLA-E and HLA-G molecules that are associated with immune tolerance, EVT also express highly polymorphic HLA-C molecules that can serve as targets for maternal dNK and CD8+ dT responses. HLA-C expression by EVT has a dual role as the main molecule to which immune tolerance needs to be established and as the only molecule that can present pathogen-derived peptides and provide protective immunity when EVT are infected. The focus of this review is to address the regulation of cytotoxicity of dNK and CD8+ dT, which is essential for maternal-fetal immune tolerance as well as recent evidence that both cell types can provide immunity to infections at the maternal-fetal interface. A particular emphasis is given to the role of HLA-C expressed by EVT and its capacity to elicit dNK and CD8+ dT responses.