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

Immune checkpoint molecules B7-1 and B7-H1 as predictive markers of pre-eclampsia: A case-control study in a Ghana

BACKGROUND/AIM

Immune tolerance in the fetal-maternal junction is maintained by a balance in the Th1/Th2 system. Th1-type immunity is associated with pro-inflammatory cytokines and immune checkpoint molecules (ICMs) such as B7-H1, while Th2-type immunity is characterized by anti-inflammatory cytokines and ICMs such as B7-1. Any imbalance in the Th1/Th2 immune system may lead to adverse pregnancy outcomes such as pre-eclampsia (PE). Hitherto, the potential of serum B7-1 and B7-H1 proteins as early markers of PE has not been explored in the Ghanaian population.

MATERIALS AND METHODS

This was a case-control study from May 2020 to April 2022 at the War Memorial and the Upper East Regional Hospitals. The study involved 291 women, including 180 (61.9%) with normotensive pregnancy and 111 (38.1%) with PE. Venous blood samples were collected and assayed for blood cell count, serum interleukins (ILs)-4, -6, -12, -18, and TNF-α as well as serum B7-1 and B7-H1 proteins.

RESULTS

The monocyte count (p = .007), the serum levels of IL-18 (p = .035), TNF-α (p = .001), and B7-H1 (p = .006) were significantly higher in PE than in normotensive pregnancy. In addition, the monocyte count (p = .002), the serum levels of IL-12 (p = .029), TNF-α (p = .016), and B7-1 (p = .009) levels were significantly higher in the third trimester than the second trimester PE. In predicting PE, the area under the curve of cytokines and ICMs ranged from 0.51 for IL-6 to 0.62 for TNF-α.

CONCLUSION

PE may be characterized by a dominant Th1-type immunity with higher levels of pro-inflammatory cytokines and B7-H1 proteins, but these variables may not be suitable for predicting PE.

Functions of LncRNAs, exosomes derived MSCs and immune regulatory molecules in preeclampsia disease

Modulatory signaling pathway such as T cell immunoreceptor with Ig and ITIM domains (TIGIT), Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA-4), P53 signaling and TIM (T-cell immunoglobin and mucin domain) are important in normal pregnancy and loss of their functions or dysregulation of related genes can lead to some disorders. Inflammation is a process by which your body's white blood cells and the things they make protect you from infection from outside invaders, such as bacteria and viruses. Some cellular and molecular signaling have been categorized to demonstrate the mechanism that protects tolerance to antigens. lncRNAs significantly impact physiological processes like immunity and metabolism, and are linked to tumors, cardiovascular diseases, nervous system disorders, and nephropathy.In this review article, we summarized recent studies about the role of TIGIT, CTLA-4, P53 and TIM regulatory molecules and reviewed dysregulation of these pathway in diseases.We will also talk about the role of lncRNAs and mesenchymal stem cells.

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.

The programmed cell death protein 1 (PD1) and the programmed cell death ligand 1 (PD-L1) are significantly downregulated on macrophages and Hofbauer cells in the placenta of preeclampsia patients

Preeclampsia is a pregnancy-specific disease which is characterized by abnormal placentation, endothelial dysfunction, systemic inflammation and disruption of the immune system. The goal of this study was to characterize the PD-1/PD-L1 system, an important immune checkpoint system, on macrophages and Hofbauer cells (HBC) in the placenta of preeclamptic patients. The expression of the macrophage markers CD68 and CD163 as well as the proteins PD1 and PD-L1 in the placenta of preeclamptic patients was examined by immunohistochemistry and immunofluorescence in comparison to the placenta of healthy pregnancies. The numbers of CD68-positive and CD163-positive macrophages were significantly downregulated in the decidua (p = 0.021 and p = 0.043) and in the chorionic villi (p < 0.001 and p < 0.001) of preeclamptic patients. The majority of macrophages in the decidua and the chorionic villi were identified to be CD163-positive, indicating a predominantly M2-polarisation. The expression of PD1 on maternal macrophages of the decidua (p < 0.001) and on Hofbauer cells (p < 0.001) was shown to be significantly lower in preeclampsia. Looking at the protein PD-L1 the expression was proven to be downregulated on maternal macrophages in the decidua of preeclamptic patients (p = 0.043). This difference was only caused by a downregulation of PD-L1 expression in male offspring (p = 0.004) while there was no difference in female offspring (p = 0.841). The variation of the immune checkpoint molecules PD1 and PD-L1 in preeclampsia might play an important role in the development of inflammation seen in preeclamptic patients. It might thereby be an important target in the therapy of preeclampsia.

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.

Excessive Immune Activation and the Correlation with Decreased Expression of PD-1 at the Maternal-Fetal Interface in Preeclampsia

The etiology of preeclampsia (PE) is still unknown, and excessive immune activation is an important component of its pathogenesis. Programmed cell death protein 1 (PD-1) is one of immune checkpoints which may prevent overactivated immune attack and lead to a tolerant immune microenvironment. Little is known about the involvement of PD-1-mediated immunoregulation at the maternal-fetal interface in PE. To investigate the inflammatory pattern and the involvement of PD-1 in the decidua of women with PE, decidual tissues were obtained from PE and control pregnant women. Quantitative RT-PCR analysis of the mRNA levels of the inflammatory cytokines was performed. PD-1 expression was detected by immunohistochemistry, western blot analysis, and flow cytometry. To prove the role of PD-1, decidual immune cells were incubated with blocking antibodies, and the inflammatory cytokines were detected by ELISA. We observed that the mRNA levels of IL-1β, IL-6, TNF-α, and IFN-γ were higher in the decidua of the PE group than in the decidua of the control group. The mRNA levels of IL-4 and IL-10 were lower in PE. The expression level of PD-1 was significantly downregulated, and the proportion (%) of PD-1 + CD45 + cells was significantly lower in PE. There was a significant linear correlation between PD-1 expression and common proinflammatory cytokines in the decidua. Anti-PD-1 blocking antibody significantly increased the secretion of proinflammatory cytokines. Our data suggested that the inflammatory pattern and decreased PD-1 expression in the decidua might play an active role in the local immunoregulatory mechanisms of PE. The PD-1 pathway in the maternal-fetal interface possibly function to break the tolerant immune microenvironment in PE via inflammatory cytokines.

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.

Expression level of immune checkpoint inhibitory factors in preeclampsia

Preeclampsia (PE) is a severe complication in pregnancy, and its symptoms (proteinuria and hypertension) manifest after 20 weeks of gestation, affecting up to 8 % of pregnancies. The pregnant women's immune system uses different tolerance mechanisms to deal with a semi-allogeneic fetus. The T-cell subsets including CD8+, CD4+, and Treg play a critical role in maintaining pregnancies. The expression of immune checkpoint molecules in T-cells can ensure pregnancy at the feto-maternal interface by controlling immune responses. This research aims to evaluate the expression level of immune checkpoint factors, including PD-1, LAG-3, CTLA-4, and TIM-3 in normal pregnant women and PE patients. Decidual tissue was collected from 50 participants (25 PE and 25 control). For evaluating the genes expression, real-time PCR was employed. The western blot was used to assess the proteins level. The results of real-time PCR indicated significantly decreased expression level of these immune checkpoints in PE patients. In parallel to gene expression results, the protein level of PD-1, LAG-3, CTLA-4, and TIM-3 in the PE group was also reduced. We revealed that the profile of proteins and genes expression of immune checkpoints in the decidua of PE mothers are different from normal pregnancy and these results indicate aberrant expression of immune checkpoints such as PD-1, LAG-3, CTLA-4, and TIM-3 may cause maladaptation immune response which results in PE manifestation.