Involvement of the Tim-3 Pathway in the Pathogenesis of Pre-Eclampsia

Investigation of immune checkpoint molecules (CTLA-4, PD-1, PD-L1, Tim-3) expressions in preeclampsia: A comparative study of membranous and soluble forms

Preeclampsia (PE) is characterized by immune dysfunction, including altered expression levels of multiple immune checkpoints (ICs), which are essential for inducing immune tolerance during pregnancy. While the pivotal role of ICs in PE is well-established, a limited understanding remains of the changes in their various forms, particularly in their membranous and secretory states. This study focused on exploring the probable role of ICs in the pathophysiology of PE via measuring the levels of their transmembrane and soluble forms. Initially, expression levels of transmembrane CTLA-4, PD-1, PD-L1, and Tim-3 on PBMCs of PE patients were assessed through qRT-PCR and western blot analysis. Additionally, ELISA was performed to evaluate their soluble forms in serum. Finally, the correlation between transmembrane and soluble forms was determined. PE patients exhibited decreased CTLA-4, PD-1, and Tim-3 expression, while PD-L1 was increased compared to the healthy group. sCTLA-4 and sPD-L1 were reduced in serum; however, sPD-1 and sTim-3 were increased. The expression of CTLA-4 on PBMCs was positively correlated with sCTLA-4. Meanwhile, PD-1, PD-L1, and Tim-3 expressions were negatively correlated with soluble forms. The observed abnormal expression levels of transmembrane CTLA-4, PD-1, PD-L1, and Tim-3 on PBMCs, along with their soluble counterparts in serum, indicate their possible role in the pathogenesis of PE. Thus, variations in these ICs' expression could enhance the differentiation of PE and aid in developing targeted therapeutic strategies.

Role of Decidual Natural Killer Cells in the Pathogenesis of Preeclampsia

Preeclampsia is one of the most severe obstetric complications, yet its pathogenesis remains unclear. Decidual natural killer (dNK) cells, the most abundant immune cells at the maternal-fetal interface, are closely associated with preeclampsia due to abnormalities in their quantity, phenotype, and function. This review summarizes the molecular mechanisms by which dNK cells regulate extravillous trophoblast (EVT) invasion, promote uterine spiral artery remodeling, and maintain immune tolerance. Furthermore, it explores how disruptions in these mechanisms and changes in the decidual microenvironment alter dNK cell properties, driving the progression of preeclampsia. Understanding the mechanisms of dNK cells and identifying potential therapeutic targets may provide new insights for clinical intervention.

Characterizing immune variation and diagnostic indicators of preeclampsia by single-cell RNA sequencing and machine learning

Preeclampsia is a multifactorial and heterogeneous complication of pregnancy. Here, we utilize single-cell RNA sequencing to dissect the involvement of circulating immune cells in preeclampsia. Our findings reveal downregulation of immune response in lymphocyte subsets in preeclampsia, such as reduction in natural killer cells and cytotoxic genes expression, and expansion of regulatory T cells. But the activation of naïve T cell and monocyte subsets, as well as increased MHC-II-mediated pathway in antigen-presenting cells were still observed in preeclampsia. Notably, we identified key monocyte subsets in preeclampsia, with significantly increased expression of angiogenesis pathways and pro-inflammatory S100 family genes in VCAN+ monocytes and IFN+ non-classical monocytes. Furthermore, four cell-type-specific machine-learning models have been developed to identify potential diagnostic indicators of preeclampsia. Collectively, our study demonstrates transcriptomic alternations of circulating immune cells and identifies immune components that could be involved in pathophysiology of preeclampsia.

A Review on Inflammasomes and Immune Checkpoints in Pre-Eclampsia Complicated with Tuberculosis and Human Immune Deficiency Virus

The current review evaluates how inflammasomes and immune checkpoints are regulated in pre-eclampsia (PE) associated with tuberculosis (TB) and Human Immune Deficiency Virus (HIV). Studies indicate that inflammasomes such as (NRLP3, NEK7, and AIM2) and immune checkpoints such as (CLT4, PD-1, TIM3, and LAG-3) are dysregulated in TB- and HIV-infected individuals, and also in pre-eclamptic pregnancies, which explains why pregnant women who are either infected with TB or HIV have an increased risk of developing PE. Evidence suggests that inhibition of inflammasomes and immune checkpoints may assist in the development of novel anti-inflammatory drugs for the prevention and management of PE in patients with or without TB and HIV infection.

Immune checkpoint inhibitors and reproductive failures

The human conceptus is a semi-allograft, which is antigenically foreign to the mother. Hence, the implantation process needs mechanisms to prevent allograft rejection during successful pregnancy. Immune checkpoints are a group of inhibitory pathways expressed on the surface of various immune cells in the form of ligand receptors. Immune cells possess these pathways to regulate the magnitude of immune responses and induce maternal-fetal tolerance. Briefly, 1) CTLA-4 can weaken T cell receptor (TCR) signals and inhibit T cell response; 2) The PD-1/PD-L1 pathway can reduce T cell proliferation, enhance T cell anergy and fatigue, reduce cytokine production, and increase T regulatory cell activity to complete the immunosuppression; 3) TIM3 interacts with T cells by binding Gal-9, weakening Th1 cell-mediated immunity and T cell apoptosis; 4) The LAG-3 binding to MHC II can inhibit T cell activation by interfering with the binding of CD4 to MHC II, and; 5) TIGIT can release inhibitory signals to NK and T cells through the ITIM structure of its cytoplasmic tail. Therefore, dysregulated immune checkpoints or the application of immune checkpoint inhibitors may impair human reproduction. This review intends to deliver a comprehensive overview of immune checkpoints in pregnancy, including CTLA-4, PD-1/PD-L1, TIM-3, LAG-3, TIGIT, and their inhibitors, reviewing their roles in normal and pathological human pregnancies.

Soluble TIM-3 as a biomarker of progression and therapeutic response in cancers and other of human diseases

Immune checkpoints inhibition is a privileged approach to combat cancers and other human diseases. The TIM-3 (T cell immunoglobulin and mucin-domain containing-3) inhibitory checkpoint expressed on different types of immune cells is actively investigated as an anticancer target, with a dozen of monoclonal antibodies in (pre)clinical development. A soluble form sTIM-3 can be found in the plasma of patients with cancer and other diseases. This active circulating protein originates from the proteolytic cleavage by two ADAM metalloproteases of the membrane receptor shared by tumor and non-tumor cells, and extracellular vesicles. In most cancers but not all, overexpression of mTIM-3 at the cell surface leads to high level of sTIM-3. Similarly, elevated levels of sTIM-3 have been reported in chronic autoimmune diseases, inflammatory gastro-intestinal diseases, certain viral and parasitic diseases, but also in cases of organ transplantation and in pregnancy-related pathologies. We have analyzed the origin of sTIM-3, its methods of dosage in blood or plasma, its presence in multiple diseases and its potential role as a biomarker to follow disease progression and/or the treatment response. In contrast to sPD-L1 generated by different classes of proteases and by alternative splicing, sTIM-3 is uniquely produced upon ADAM-dependent shedding, providing a more homogenous molecular entity and a possibly more reliable molecular marker. However, the biological functionality of sTIM-3 remains insufficiently characterized. The review shed light on pathologies associated with an altered expression of sTIM-3 in human plasma and the possibility to use sTIM-3 as a diagnostic or therapeutic marker.

Contribution of the TIM-3/Gal-9 immune checkpoint to tropical parasitic diseases

Neglected tropical parasitic diseases (NTD) are prevalent in many countries and cost-effective treatments remain urgently needed. Novel approaches have been proposed to address these diseases through an action on immune co-inhibitory checkpoints which are exploited by parasites to evade the immune system. Among these checkpoints, TIM-3 has been shown to play a key role in antiparasitic immunity via a repression and functional attenuation of CD4⁺ and/or CD8⁺ T-cells. The present review discusses the role of the TIM-3/galectin-9 checkpoint in seven major NTD: Chagas disease, leishmaniasis and malaria (3 trypanosomatid infections), schistosomiasis, toxoplasmosis, echinococcosis and filariasis (4 helminth infections). In each case, the role of the checkpoint has been analyzed and the use of anti-TIM-3 antibodies evaluated as a potential therapeutic approach. In general, the parasitic infection is coupled with an upregulation of TIM-3 expressed on T cells, but not necessarily with an exhaustion of those T cells. In several cases, the use of anti-TIM-3 antibodies represent a possible strategy to reinforce the clearance and to reduce the parasite load. Promising data have been reported in cases of leishmaniasis, malaria and schistosomiasis, whereas a similar approach proved much less efficient (if not deleterious) in cases of echinococcosis and the Chagas disease. Nevertheless, the TIM-3 checkpoint warrants further consideration as a potential immune target to combat these pathologies, using antibodies or drugs capable of reducing directly or indirectly the expression and function of the checkpoint, to restore an immune control.

Phenotypic and functional alteration of CD45+ immune cells in the decidua of preeclampsia patients analyzed by mass cytometry (CyTOF)

Preeclampsia (PE) is a severe placenta-related pregnancy disease that has been associated with maternal systemic inflammation and immune system disorders. However, the distribution and functional changes in immune cells of the maternal-placental interface have not been well characterized. Herein, cytometry by time-of-flight mass spectrometry (CyTOF) was used to investigate the immune atlas at the decidua, which was obtained from four PE patients and four healthy controls. Six superclusters were identified, namely, T cells, B cells, natural killer (NK) cells, monocytes, granulocytes, and others. B cells were significantly decreased in the PE group, among which the reduction in CD27+CD38+ regulatory B cell (Breg)-like cells may stimulate immune activation in PE. The significantly increased migration of B cells could be linked to the significantly overexpressed chemokine C-X-C receptor 5 (CXCR5) in the PE group, which may result in the production of excessive autoantibodies and the pathogenesis of PE. A subset of T cells, CD11c+CD8+ T cells, was significantly decreased in PE and might lead to sustained immune activation in PE patients. NK cells were ultimately separated into four subsets. The significant reduction in a novel subset of NK cells (CD56-CD49a-CD38+) in PE might have led to the failure to suppress inflammation at the maternal-fetal interface during PE progression. Moreover, the expression levels of functional markers were significantly altered in the PE group, which also inferred that shifts in the decidual immune state contributed to the development of PE and might serve as potential treatment targets. This is a worthy attempt to elaborate the differences in the phenotype and function of CD45+ immune cells in the decidua between PE and healthy pregnancies by CyTOF, which contributes to understand the pathogenesis of PE, and the altered cell subsets and markers may inspire the immune modulatory therapy for PE.

Tim-3 downregulation by Toxoplasma gondii infection contributes to decidual dendritic cell dysfunction

Background

Women in early pregnancy infected by Toxoplasma gondii may have severe adverse pregnancy outcomes, such as spontaneous abortion and fetal malformation. The inhibitory molecule T cell immunoglobulin and mucin domain 3 (Tim-3) is highly expressed on decidual dendritic cells (dDCs) and plays an important role in maintaining immune tolerance. However, whether T. gondii infection can cause dDC dysfunction by influencing the expression of Tim-3 and further participate in adverse pregnancy outcomes is still unclear.

Methods

An abnormal pregnancy model in Tim-3-deficient mice and primary human dDCs treated with Tim-3 neutralizing antibodies were used to examine the effect of Tim-3 expression on dDC dysfunction after T. gondii infection.

Results

Following T. gondii infection, the expression of Tim-3 on dDCs was downregulated, those of the pro-inflammatory functional molecules CD80, CD86, MHC-II, tumor necrosis factor-α (TNF-α), and interleukin-12 (IL-12) were increased, while those of the tolerant molecules indoleamine 2,3-dioxygenase (IDO) and interleukin-10 (IL-10) were significantly reduced. Tim-3 downregulation by T. gondii infection was closely associated with an increase in proinflammatory molecules and a decrease in tolerant molecules, which further resulted in dDC dysfunction. Moreover, the changes in Tim-3 induced by T. gondii infection further reduced the secretion of the cytokine IL-10 via the SRC-signal transducer and activator of transcription 3 (STAT3) pathway, which ultimately contributed to abnormal pregnancy outcomes.

Conclusions

Toxoplasma gondii infection can significantly downregulate the expression of Tim-3 and cause the aberrant expression of functional molecules in dDCs. This leads to dDC dysfunction, which can ultimately contribute to abnormal pregnancy outcomes. Further, the expression of the anti-inflammatory molecule IL-10 was significantly decreased by Tim-3 downregulation, which was mediated by the SRC-STAT3 signaling pathway in dDCs after T. gondii infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05506-1.

Expression of inhibitory receptors PD-1, CTLA-4, and Tim-3 by peripheral T cells during pregnancy

Background. Inhibitory receptors and their ligands (also called checkpoint molecules) are important feedback regulators of the immune response. However, their role in immunological adaptation during pregnancy remains poorly understood.

The aim of the study was to evaluate the level of checkpoint molecule (PD-1, CTLA-4, Tim-3) expression in peripheral T cells in pregnant women compared with fertile non-pregnant women.

Materials and methods. The study included 36 women in the second half of pregnancy without pregnancy complications, 12 of whom had extragenital pathology. The control group consisted of 28 age-matched fertile non-pregnant women. The proportion of CD8+PD-1+, CD8+TIM-3+, CD8+PD-1+TIM-3+, CD4+PD-1+, CD4+TIM-3+, and CD4+PD-1+TIM-3+ was evaluated by flow cytometry using the corresponding monoclonal antibodies (BD Biosciences, USA).

Results. The proportion of CD4+Tim-3+ and CD8+PD-1+ Т cells and CD4+ and CD8+ Т lymphocytes co-expressing PD-1 and Tim-3 in the peripheral blood of pregnant women was statistically significantly higher than in non-pregnant women. An increase in CD4+Tim-3+ and CD8+PD-1+ T cells was observed both in pregnant women with and without extragenital pathology. However, pregnant women with extragenital pathology were characterized by a higher CD8+PD-1+ count and a smaller number of CD8+Tim-3+ cells, as well as by a lack of an increase in PD-1+Tim-3+ T cells typical of pregnant women. The number of comorbidities was directly correlated with the proportion of CD8+PD-1+ lymphocytes and inversely correlated with the proportion of CD8+Tim-3+ and CD4+ PD-1+Tim-3+ cells. In addition, the expression of checkpoint molecules was associated with gestational age (a direct correlation was found with the proportion of CD8+Tim-3+, CD4+PD-1+Tim-3+, and CD8+PD-1+Tim-3+ cells) and to a lesser extent – with the age of pregnant women (an inverse relationship was found with the proportion of CD8+Tim-3+ cells).

Conclusion. Pregnant women in the second half of pregnancy are characterized by increased expression of PD-1 and Tim-3 molecules in peripheral T cells. At the same time, concomitant extragenital pathology affects the expression of these molecules.

The Role of the Immune Checkpoint Molecules PD-1/PD-L1 and TIM-3/Gal-9 in the Pathogenesis of Preeclampsia—A Narrative Review

Preeclampsia is a pregnancy-specific disease which is characterized by abnormal placentation, endothelial dysfunction, and systemic inflammation. Several studies have shown that the maternal immune system, which is crucial for maintaining the pregnancy by ensuring maternal-fetal-tolerance, is disrupted in preeclamptic patients. Besides different immune cells, immune checkpoint molecules such as the programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1 system) and the T-cell immunoglobulin and mucin domain-containing protein 3/Galectin-9 (TIM-3/Gal-9 system) are key players in upholding the balance between pro-inflammatory and anti-inflammatory signals. Therefore, a clear understanding about the role of these immune checkpoint molecules in preeclampsia is essential. This review discusses the role of these two immune checkpoint systems in pregnancy and their alterations in preeclampsia.

Regulation of the innate immune cells during pregnancy: An immune checkpoint perspective

The foetus can be regarded as a half‐allograft implanted into the maternal body. In a successful pregnancy, the mother does not reject the foetus because of the immune tolerance mechanism at the maternal‐foetal interface. The innate immune cells are a large part of the decidual leukocytes contributing significantly to a successful pregnancy. Although the contributions have been recognized, their role in human pregnancy has not been completely elucidated. Additionally, the accumulated evidence demonstrates that the immune checkpoint molecules expressed on the immune cells are co‐inhibitory receptors regulating their activation and biological function. Therefore, it is critical to understand the immune microenvironment and explore the function of the innate immune cells during pregnancy. This review summarizes the classic immune checkpoints such as PD‐1, CTLA‐4 and some novel molecules recently identified, including TIM‐3, CD200, TIGIT and the Siglecs family on the decidual and peripheral innate immune cells during pregnancy. Furthermore, it emphasizes the role of the immune checkpoint molecules in pregnancy‐associated complications and reproductive immunotherapy.