Soluble T cell immunoglobulin mucin domain 3 (sTim-3) in maternal sera: a potential contributor to immune regulation during pregnancy

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.

Associations of Th1, Th2, Th17, and Treg cell levels and imbalance with recurrent spontaneous abortion: A meta-analysis

OBJECTIVE

Abnormal levels and imbalances of T cell subsets are common in recurrent spontaneous abortion (RSA) patients, but most studies have small sample sizes, and comprehensive evaluations are lacking. Therefore, this meta-analysis aimed to comprehensively investigate T cell subsets and their ratios in RSA patients.

METHODS

Four databases (PubMed, EMBASE, Web of Science, and Cochrane Library databases) were searched until 10 January 2024. T helper 1 (Th1), Th2, Th1/Th2 ratio, Th17, regulatory T (Treg), Treg/Th17 ratio, and the correlation between Th17 and Treg were considered endpoint indexes.

RESULTS

Twenty-six studies involving 1143 RSA women (RSA group) and 863 healthy women (healthy control group) were included. Th1 (standardized mean difference [SMD] = 0.603%; 95% confidence intervals [CI]: 0.406%, 0.800%; p < 0.001), Th1/Th2 ratio (SMD = 0.838; 95% CI: 0.364, 1.312; p = 0.001), and Th17 (SMD = 1.047%; 95% CI: 0.734%, 1.360%; p < 0.001) increased; Th2 (SMD = -0.719%; 95% CI: -1.263%, -0.174%; p = 0.010), Treg (SMD = -1.176%; 95% CI: -1.755%, -0.596%; p < 0.001) and Treg/Th17 ratio (SMD = -0.978; 95% CI: -1.576, -0.381; p = 0.001) reduced in RSA group versus healthy control group. Th17 were inversely correlated with Treg in RSA patients (Correlation coefficient = -0.488; 95% CI: -0.726, -0.145; p = 0.019). The risk of bias was relatively low. There was no publication bias for Th1, Th2, or Th1/Th2 ratio; publication biases for other outcomes were corrected by the trim-and-fill method. Sensitivity analyses showed relatively high robustness.

CONCLUSION

Th1, Th1/Th2 ratio, and Th17 are elevated, while Th2, Treg, and Treg/Th17 ratio are reduced in RSA patients. Meanwhile, Th17 was inversely correlated with Treg in these patients.

Soluble Forms of Immune Checkpoints and Their Ligands as Potential Biomarkers in the Diagnosis of Recurrent Pregnancy Loss-A Preliminary Study

Immune checkpoints (ICPs) serve as regulatory switches on immune-competent cells. Soluble ICPs consist of fragments derived from ICP molecules typically located on cell membranes. Research has demonstrated that they perform similar functions to their membrane-bound counterparts but are directly present in the bloodstream. Effective control of the maternal immune system is vital for a successful pregnancy due to genetic differences between the mother and fetus. Abnormalities in the immune response are widely acknowledged as the primary cause of spontaneous abortions. In our research, we introduce a novel approach to understanding the immune-mediated mechanisms underlying recurrent miscarriages and explore new possibilities for diagnosing and preventing pregnancy loss. The female participants in the study were divided into three groups: RSA (recurrent spontaneous abortion), pregnant, and non-pregnant women. The analysis of soluble forms of immune checkpoints and their ligands in the serum of the study groups was conducted using the Luminex method Statistically significant differences in the concentrations of (ICPs) were observed between physiological pregnancies and the RSA group. Among patients with RSA, we noted reduced concentrations of sGalectin-9, sTIM-3, and sCD155, along with elevated concentrations of LAG-3, sCD80, and sCD86 ICPs, in comparison to physiological pregnancies. Our study indicates that sGalectin-9, TIM-3, sLAG-3, sCD80, sCD86, sVISTA, sNectin-2, and sCD155 could potentially serve as biological markers of a healthy, physiological pregnancy. These findings suggest that changes in the concentrations of soluble immune checkpoints may have the potential to act as markers for early pregnancy loss.

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.

Persistent T-cell exhaustion in relation to prolonged pulmonary pathology and death after severe COVID-19: Results from two Norwegian cohort studies

BACKGROUND

T-cell activation is associated with an adverse outcome in COVID-19, but whether T-cell activation and exhaustion relate to persistent respiratory dysfunction and death is unknown.

OBJECTIVES

To investigate whether T-cell activation and exhaustion persist and are associated with prolonged respiratory dysfunction and death after hospitalization for COVID-19.

METHODS

Plasma and serum from two Norwegian cohorts of hospitalized patients with COVID-19 (n = 414) were analyzed for soluble (s) markers of T-cell activation (sCD25) and exhaustion (sTim-3) during hospitalization and follow-up.

RESULTS

Both markers were strongly associated with acute respiratory failure, but only sTim-3 was independently associated with 60-day mortality. Levels of sTim-3 remained elevated 3 and 12 months after hospitalization and were associated with pulmonary radiological pathology after 3 months.

CONCLUSION

Our findings suggest prolonged T-cell exhaustion is an important immunological sequela, potentially related to long-term outcomes after severe COVID-19.

Next generation of immune checkpoint molecules in maternal-fetal immunity

Successful pregnancy is a unique situation requires the maternal immune system to recognize and tolerate a semi-identical fetus and allow normal invasion of trophoblast cells. Although efforts have been made, the deep mechanisms of the maternal-fetal crosstalk have not yet been fully deciphered. Immune checkpoint molecules (ICMs) are a group of negative modulators of the immune response that avoid immune damage. They have been extensively studied in the fields of oncology and transplantation, while the latest evidence suggests that they are closely associated with pregnancy outcomes via multiple inhibitory mechanisms. Although studies have mostly demonstrated the regulatory role of the well-known PD-1, CTLA-4 at the maternal-fetal interface, what is unique about the newly discovered multiple ICMs remains a mystery. Here, we review the latest knowledge on ICMs, focusing on the first generation of checkpoints (PD-1, CTLA-4) and the next generation (Tim-3, Tigit, Lag-3, VISTA) highlighting their immunoregulatory roles in maternal-fetal tolerance and decidual vascular remodeling, and their involvement in pathological pregnancies. The content covers three aspects: the characteristics they possess, the dynamic expression profile of their expression at the maternal-fetal interface, and their involvement in pathological pregnancy. In immunotherapy strategies for pregnancy complications, upregulation of immune checkpoints may play a role. Meanwhile, the impact on pregnancy outcomes when using ICMs in clinical cancer treatment during pregnancy is a topic worth exploring. These may serve as a guide for future basic research and clinical applications of maternal-fetal immunity.

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.

Immune checkpoints and reproductive immunology: Pioneers in the future therapy of infertility related Disorders?

As co-stimulatory receptors, immune checkpoint molecules are found on the surface of various immune cells and transduce inhibitory signals following ligand binding. The most studied members in this regard include PD-1, TIM-3, and CTLA-4. The physiological part immune checkpoints possess is the prevention of dangerous immune attacks towards self-antigens throughout an immune response, which takes place through the negative regulation of the effector immune cells, through the induction of T-cell exhaustion, for instance. It has recently been suggested that each checkpoint reduces immunoactivation via distinct intracellular mechanisms of signaling. Regulators of immune checkpoints are supposed to participate actively in immune defense mechanisms against infections, preventing autoimmunity, transplantation, and tumor immune evasion. In pregnancy, as an active immunotolerance mechanism which is also natural, the maternal immune system encounters two simultaneous challenges; in addition to accepting the semi-allogeneic fetus, the maternal immune system should also prevent infections. In this regard, the part immune checkpoint molecules possess is particularly interesting. Herein, the current understanding of such part in reproductive immunology is described.