Induced Treg Cells Augment the Th17-Mediated Intestinal Inflammatory Response in a CTLA4-Dependent Manner

Current research insights into the role of CTLA-4 in hepatitis B virus (HBV) infection

Chronic hepatitis B virus (HBV) infection is a significant global public health concern, and the clearance of HBV is closely linked to the activity of HBV-specific T cells, which is regulated by various co-suppressor molecules. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is among these co-suppressor molecules which induces T cell exhaustion by competitively inhibiting CD28 and dampening the function of HBV-specific T cells. CTLA-4 also plays a role in the regulation of T helper (Th) cell differentiation and influences cytokine release. In addition, CTLA-4 can impact glucose metabolism in hepatocellular carcinoma through its interaction with T regulatory (Treg) cells. This review aims to provide a comprehensive overview of the existing literature related to the role of CTLA-4 in HBV patients across different subsets of T cells. Additionally, we propose a discussion on the possible mechanisms through which CTLA-4 may contribute to HBV infection, as well as the development of HBV-induced cirrhosis and hepatocellular carcinoma.

Generation of reporter mice for detecting the transcriptional activity of nuclear factor of activated T cells

Nuclear factor of activated T cells (NFAT) is a transcription factor essential for immunological and other biological responses. To develop analyzing system for NFAT activity in vitro and in vivo, we generated reporter mouse lines introduced with NFAT-driven enhanced green fluorescent protein (EGFP) expressing gene construct. Six tandem repeats of -286 to -265 of the human IL2 gene to which NFAT binds in association with its co-transcription factor, activator protein (AP)-1, was conjunct with thymidine kinase minimum promoter and following EGFP coding sequence. Upon introduction of the resulting reporter cassette into C57BL/6 fertilized eggs, the transgenic mice were obtained. Among 7 transgene-positive mice in 110 mice bone, 2 mice showed the designated reporter mouse character. Thus, the EGFP fluorescence of CD4+ and CD8+ T cells in these mice was enhanced by stimulation through CD3 and CD28. Each of phorbol 12-myristate 13-acetate (PMA) and ionomycin (IOM) stimulation weakly but their combined stimulation strongly enhanced EGFP expression. The stimulation-induced EGFP upregulation was also observed following T cell subset differentiation in a different manner. The EGFP induction by PMA + IOM stimulation was more potent than that by CD3/CD28 stimulation in helper T (Th)1, Th2, Th9, and regulatory T cells, while both stimulation conditions displayed the equivalent EGFP induction in Th17 cells. Our NFAT reporter mouse lines are useful for analyzing stimulation-induced transcriptional activation mediated by NFAT in cooperation with AP-1 in T cells.

Expression and Function of Nicotinic Acetylcholine Receptors in Induced Regulatory T Cells

A contribution of the cholinergic system to immune cell function has been suggested, though the role of nicotine and its receptors in T cells, especially regulatory T (Treg) cells, is unclear. We herein investigated the expression and function of nicotinic acetylcholine receptors (nAChRs) in murine-induced Treg (iTreg) cells. Upon differentiation of naive BALB/c T cells into iTreg cells and other T-cell subsets, the effect of nicotine on cytokine production and proliferation of iTreg cells was examined. The expression of nAChRs and its regulatory mechanisms were comparatively analyzed among T-cell subsets. Stimulation-induced transforming growth factor-β1 (TGF-β1) production of iTreg cells was suppressed by nicotine, whereas interleukin (IL)-10 production and proliferation was not affected. α2-, α5-, α9-, and β2-nAChRs were differentially expressed in naive, Th1, Th2, Th9, Th17, and iTreg cells. Among these cell types, the α9-nAChR was particularly upregulated in iTreg cells via its gene promoter, but not through tri-methylation at the 4th lysine residue of the histone H3-dependent mechanisms. We conclude that the immunoregulatory role of Treg cells is modified by the cholinergic system, probably through the characteristic expression of nAChRs.

L-type amino acid transporter 1 inhibitor suppresses murine Th2 cell-mediated bronchial hyperresponsiveness independently of eosinophil accumulation

Background

The activation of Th2 cells that play a pivotal role in the development of allergic eosinophilic inflammation is regulated by an L-type amino acid transporter (LAT) 1. However, the contribution of LAT1 to the pathogenesis of Th2 cell-mediated airway inflammation has not been investigated.

Objective

In this study, we investigated the effect of a LAT1 inhibitor, JPH203, on Th2 cell-mediated airway eosinophilic inflammation.

Methods

BALB/c mice were transferred with ovalbumin (OVA)-specific Th2 cell and challenged by corresponding allergen with or without administration of JPH203. Then, the infiltration of inflammatory cells including eosinophils and allergen-specific Th2 cells in the lungs and bronchial hyperresponsiveness (BHR) was assessed.

Results

Inflammatory responses in the lungs with massive accumulation of eosinophils and BHR were induced in Th2 cell-transferred mice upon challenge with OVA. The treatment with JPH203 significantly suppressed the allergen-induced BHR but not eosinophil infiltration. The infused Th2 cells were also accumulated in the lungs upon allergen challenge, though the response was not affected by JPH203 treatment.

Conclusion

JPH203 suppressed Th2 cell-mediated BHR through the mechanisms independently of the lung accumulation of eosinophils and Th2 cells.

MSC-like cells increase ability of monocyte-derived dendritic cells to polarize IL-17-/IL-10-producing T cells via CTLA-4

Mesenchymal stromal cell-like (MSCl) cells generated from human embryonic stem cells are considered to be an eligible cell line to model the immunomodulatory behavior of mesenchymal stromal cells (MSCs) in vitro. Dendritic cells (DCs) are essential players in the maintenance and restoration of the sensitive balance between tolerance and immunity. Here, the effects of MSCl cells on the in vitro differentiation of human monocytes into DCs were investigated. MSCl cells promote the differentiation of CTLA-4 expressing DCs via the production of all-trans retinoic acid (ATRA) functioning as a ligand of RARα, a key nuclear receptor in DC development. These semi-matured DCs exhibit an ability to activate allogeneic, naive T cells and polarize them into IL-10 + IL-17 + double-positive T helper cells in a CTLA-4-dependent manner. Mapping the molecular mechanisms of MSC-mediated indirect modulation of DC differentiation may help to expand MSCs' clinical application in cell-free therapies.

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Mesenchymal stromal cell-like cells alter moDC differentiation via RARα activation

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Mesenchymal stromal cell-like cells express genes known to play role in ATRA synthesis

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MoDCs, differentiated in the presence of MSCl-derived factors, express CTLA-4

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CTLA-4⁺ moDCs are able to induce polarization of IL-10- and IL-17-producing helper T cells

CEACAM1 regulates CD8+ T cell immunity and protects from severe pathology during Citrobacter rodentium induced colitis

The incidence of gastrointestinal infections continues to increase, and infectious colitis contributes significantly to morbidity and mortality worldwide. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) has been discovered to be strongly involved in the intestinal homeostasis. However, whether intestinal CEACAM1 expression has an impact on the control of infectious colitis remains elusive. Citrobacter rodentium (C. rodentium) is a gram-negative enteric pathogen that induces colonic inflammation in mice, with a critical role for CD4+ T cell but not CD8+ T cell immunity to primary infection. Here, we show that Ceacam1-/- mice are much more susceptible to C. rodentium infection than wildtype mice, which is mediated by a defect in the intestinal barrier and, surprisingly, by a dysregulated CD8+ T cell but not CD4+ T cell response in the colon. CEACAM1 expression is essential for the control of CD8+ T cell immunity, as CEACAM1 deficiency during C. rodentium infection inhibits CD8+ T cell exhaustion. We conclude that CEACAM1 is an important regulator of CD8+ T cell function in the colon, and blocking CEACAM1 signaling to activate CD8+ T cells may have unforeseen side effects.

Fractalkine mediates lymphocyte inflammation and tubulointerstitial lesions by modifying the Treg/Th17 balance in lupus-prone MRL/lpr mice

In this study, we first analyzed the expression level of fractalkine (FKN) in the serum of patients with lupus nephritis (LN) and the distribution of peripheral blood Treg cells, and explored FKN and Treg cells, systemic lupus erythematosus disease activity index 2000 (SLEDAI-2K) correlation. Subsequently, we explored the specific role of FKN in tubule interstitial lesions (TILs) and regulatory T (Treg) cells/T helper (Th) 17 cell balance in lupus model mice. Treated with an anti-FKN antibody (aFKN), recombinant FKN (rFKN), or an isotype antibody (IgG) in MRL/MpJ-Faslpr/J and C57BL/6 mice, and then detected TIL level and forkhead box p3 (Foxp3), IL-10, IL-17 and IL-6 expression levels in the kidney and spleen in the proportion of Treg and Th17 cells. Finally, then use aFKN, rFKN, or IgG to intervene in polarized Tregs with IL-6, TGF-β, IL-23, anti-interferon, and Th17 cells with anti-IL-4 after transforming to transform growth factor (TGF)-β and interleukin (IL)-2 in isolated mouse spleen lymphocytes. The results showed that the expression level of FKN was positively correlated with SLEDAI-2K and negatively correlated with the distribution of Treg cells. After treatment with aFKN in lupus model mice, kidney damage was delayed, TIL formation was reduced, Foxp3 and IL-10 levels were up-regulated, IL-17 and IL-6 levels were down-regulated in renal tissues, Th17 cell subsets and Treg cell subsets were reduced The increase is in the spleen, and rFKN treatment has the opposite effect in mouse. In addition, after interfering with polarized cells by aFKN, it was found that IL-17 and IL-6 expression levels were down-regulated in Th17 cells, Foxp3 and IL-10 levels in Tregs were up-regulated, and rFKN treatment had the opposite effect in vitro. These results indicate that FKN participates in and promotes SLE target organ damage including: secretion of inflammatory factors and renal TIL, and most importantly, these effects might have been due to modification of the Treg/Th17 cell balance.

Role of CD4+ T Cells in Allergic Airway Diseases: Learning from Murine Models

The essential contribution of CD4⁺ T cells in allergic airway diseases has been demonstrated, especially by using various murine models of antigen-induced airway inflammation. In addition to antigen-immunized mouse models employing mast cell-deficient mice and CD4⁺ T cell-depleting procedure, antigen-specific CD4⁺ T cell transfer models have revealed the possible development of allergic inflammation solely dependent on CD4⁺ T cells. Regardless of the classical Th1/Th2 theory, various helper T cell subsets have the potential to induce different types of allergic inflammation. T cell receptor (TCR)-transgenic (Tg) mice have been used for investigating T cell-mediated immune responses. Besides, we have recently generated cloned mice from antigen-specific CD4⁺ T cells through somatic cell nuclear transfer. In contrast to TCR-Tg mice that express artificially introduced TCR, the cloned mice express endogenously regulated antigen-specific TCR. Upon antigen exposure, the mite antigen-reactive T cell-cloned mice displayed strong airway inflammation accompanied by bronchial hyperresponsiveness in a short time period. Antigen-specific CD4⁺ T cell-cloned mice are expected to be useful for investigating the detailed role of CD4⁺ T cells in various allergic diseases and for evaluating novel anti-allergic drugs.

Sarcoidosis and the mTOR, Rac1, and Autophagy Triad

Sarcoidosis is an enigmatic multisystem disease characterized by the development and accumulation of granulomas: a compact collection of macrophages that have differentiated into epithelioid cells and which are associated with T helper (Th)1 and Th17 cells. Although no single causative factor has been shown to underlie sarcoidosis in humans, its etiology has been related to microbial, environmental, and genetic factors. We examine how these factors play a role in sarcoidosis pathogenesis. Specifically, we propose that dysfunction of mTOR, Rac1, and autophagy-related pathways not only hampers pathogen or nonorganic particle clearance but also participates in T cell and macrophage dysfunction, driving granuloma formation. This concept opens new avenues for potentially treating sarcoidosis and may serve as a blueprint for other granulomatous disorders.

Regulatory T-cells promote pulmonary repair by modulating T helper cell immune responses in lipopolysaccharide-induced acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) induces a strong local infiltration of regulatory T-cells (Tregs) in the lungs. However, at present, there remains a lack of adequate evidence showing the direct effect of Tregs on pulmonary repair and the related mechanisms of ARDS. Therefore, in this project, we studied the impact of Tregs on lipopolysaccharide (LPS)-induced ARDS and pulmonary inflammation. Surprisingly, we found that depletion of Tregs by injection of PC61 anti-CD25 antibody not only interfered with the inflammation resolution, such as inhibited total cell infiltration into the alveolar space, downregulated neutrophils, upregulated macrophages, but also impaired pulmonary epithelium and endothelial cell proliferation. Consistent with the attenuation of pulmonary repair, we found that the Th1 and Th17 immune responses were also impaired in Treg-depleted mice, suggesting that the presence of Tregs is vital for tissue repair, as Tregs modulate and promote the Th immune response in LPS-induced pulmonary inflammation.

Differential Contribution of Adhesion Molecules to Th1 and Th2 Cell-Mediated Lung and Bowel Inflammation

CD4⁺ T cells play a critical role in the development of allergic inflammation in several target organs. Various adhesion molecules are involved in the local recruitment of T cells and other inflammatory cells. We investigated the differential contribution of adhesion molecules to T helper 1 (Th1) and Th2 cell-mediated allergic lung and bowel inflammation by employing their neutralizing antibodies. BALB/c mice transferred with in vitro-differentiated antigen-specific Th1 and Th2 cells were intratracheally or intrarectally challenged with a relevant antigen. Infiltration of infused T cells occurred, along with the accumulation of neutrophils and eosinophils in the lungs of Th1 and Th2 cell-transferred recipients, respectively. Th1-mediated neutrophil and Th2-mediated eosinophil accumulation in the large intestine, which occurred after intrarectal challenge with the antigen, was indicated by the significant elevation of myeloperoxidase (MPO) and eosinophil peroxidase (EPO) activity. Blocking experiments with neutralizing antibodies indicated that intercellular cell adhesion molecule (ICAM)-1; vascular cell adhesion molecule (VCAM)-1; and αL, β2, and β7 integrins participate in the accumulation of Th2 cells and eosinophils in the lungs. In contrast, the migration of Th1 cells and neutrophils was diminished by blockage of αL/β2-integrin and ICAM-1, respectively. Mucosal addressin cell adhesion molecule (MadCAM)-1, vascular cell adhesion molecule (VCAM)-1, α4, β1, and β7 contributed to Th1-mediated neutrophilic inflammation in the bowel, though only MadCAM-1, α4, αL, and β2 were involved in Th2-mediated eosinophilic inflammation. We conclude that distinct sets of adhesion molecules are involved in Th1- and Th2-mediated allergic lung and bowel inflammation.

Efficacy of anti-IL-23 monotherapy versus combination therapy with anti-IL-17 in estrogen deficiency induced bone loss conditions

Recent studies have identified that Interleukin (IL)-23/IL-17 axis plays crucial role in pathogenesis of inflammation and bone destruction. IL-23 is thought to promote joint destruction in arthritis by stimulating Th17 cells. IL-23 directly mediates bone loss by inducing osteoclastogenesis and receptor activator of kappa B ligand (RANKL) expression in T cells. IL-23 also promotes tartrate-resistant acid phosphatase (TRAP) activity of osteoclast in osteoblast-osteoclast co-culture. The role of IL-23 has not been studied in estrogen deficiency induced bone loss. Here, we study the effect of IL-23 neutralization in ovariectomized (Ovx) estrogen deficient mice on various immune and skeletal parameters. We also determine whether the combination of anti-IL-23 and anti-IL17 has enhanced osteoprotective effects compared to monotherapies. Treatment of anti-IL-23 and its combination with anti-IL-17 suppressed Th17 cell differentiation and promoted development of T regulatory cells. Anti-IL-23 and its combination with anti-IL-17 prevented bone loss. However, the individual monotherapies of anti-IL-23 and anti-IL-17 were more effective than combination therapy. Treatment of IL-17 and IL-23 cytokines to bone marrow stromal cells led to increased differentiation towards osteoblast lineage. Double neutralization of IL-23 and IL-17 might be inhibiting this phenomenon thus producing less potent effects. Our studies thus support bone protective effects of anti-IL-23 and that the monotherapies of neutralizing antibodies against IL-17 and IL-23 may be a more accepted mode of treatment in management of post-menopausal bone loss rather than combination therapy.

T-Helper Type 2 Cells Direct Antigen-Induced Eosinophilic Skin Inflammation in Mice

Eosinophilic inflammation in combination with immunoglobulin E (IgE) production is a characteristic feature of atopic dermatitis. Although activated T-helper type (Th) 2 cells play critical roles in the local accumulation and activation of eosinophils, whether they induce eosinophilic skin inflammation, independent of the IgE-mediated pathway has been unclear. To address the functional role of T cells in allergic skin diseases, we herein transferred Th1/Th2-differentiated or naive DO11.10 T cells into unprimed BALB/c mice. Ovalbumin-specific Th2 cells, as well as eosinophils, accumulated in the skin upon antigen challenge, despite the absence of antigen-specific IgE. Neither antigen-specific Th1 nor naive T cells induced eosinophil accumulation, although Th1 cells by themselves migrated into the skin. Interleukin (IL)-4, IL-5, and eotaxin were specifically produced in the skin of antigen-challenged, Th2 cell-transferred mice, whereas interferon (IFN)-γ and regulated on activation, normal T cell expressed and secreted (RANTES) were preferentially produced in Th1 cells-transferred mice. Production of monocyte chemoattractant protein (MCP)-1 and MCP-3 was enhanced by both Th1 and Th2 cells. The accumulation of eosinophils and Th2 cells in the skin was suppressed by both dexamethasone and FK506, indicating an essential role of Th2 cells in eosinophil recruitment. We conclude that Th2 cells can induce eosinophilic infiltration into the skin in the absence of antigen-specific IgE.

Contribution of neuraminidase 3 to the differentiation of induced regulatory T cells

Neuraminidase family enzymes that hydrolyze the terminal sialic acid linkage in biomolecules are involved in various immune responses. We previously showed that Th1 and Th2 cells differentially express several neuraminidases. Herein, the expression of neuraminidases in induced regulatory T (iTreg) cells was investigated in comparison with that in other T-cell subsets. Contrary to the tendency toward higher neuraminidase 1 mRNA expression in in vitro-differentiated Th2 cells, compared to Th1, Th17 and iTreg cells, we observed significantly higher expression of neuraminidase 3 (Neu3) in iTreg cells. Furthermore, the expression of Neu3 in FoxP3⁺ CD62L^- spleen cells was higher than that in FoxP3⁺ CD62L⁺ and FoxP3^- cells. Lentiviral expression of Neu3 in naïve CD4⁺ T cells during the stimulation culture led to upregulation of FoxP3 expression. On the basis of these findings, we conclude that Neu3 contributes to the differentiation of iTreg cells by upregulation of FoxP3.

T-cell expression of AhR inhibits the maintenance of pTreg cells in the gastrointestinal tract in acute GVHD

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that affects the function and development of immune cells. Here, we show that recipient mice receiving AhR^-/- T cells have improved survival and decreased acute graft-versus-host disease (aGVHD) in 2 different murine allogeneic bone marrow transplant (BMT) models. We also show that CD4⁺ T cells lacking AhR demonstrate reduced accumulation in secondary lymphoid tissue because of low levels of proliferation 4 days after BMT. Additionally, we found a significant increase in the quantity of peripherally induced regulatory donor T (pT_reg) cells in the colon of recipients transplanted with AhR^-/- T cells 14 days after transplant. Blockade of AhR using a clinically available AhR antagonist greatly enhanced the in vitro generation of inducible T_reg (iT_reg) cells from naïve CD4⁺ human T cells. We have identified AhR as a novel target on donor T cells that is critical to the pathogenesis of aGVHD.

CEACAM1 as a multi-purpose target for cancer immunotherapy

CEACAM1 is an extensively studied cell surface molecule with established functions in multiple cancer types, as well as in various compartments of the immune system. Due to its multi-faceted role as a recently appreciated immune checkpoint inhibitor and tumor marker, CEACAM1 is an attractive target for cancer immunotherapy. Herein, we highlight CEACAM1's function in various immune compartments and cancer types, including in the context of metastatic disease. This review outlines CEACAM1's role as a therapeutic target for cancer treatment in light of these properties.