Control of the differentiation of regulatory T cells and T(H)17 cells by the DNA-binding inhibitor Id3

Regulatory T cells and IFN-γ-producing Th1 cells play a critical role in the pathogenesis of Sjögren's Syndrome

Objectives

Sjögren's Disease (SjD) is an autoimmune disorder characterized by progressive dysfunction, inflammation and destruction of salivary and lacrimal glands, and by extraglandular manifestations. Its etiology and pathophysiology remain incompletely understood, though a role for autoreactive B cells has been considered key. Here, we investigated the role of effector and regulatory T cells in the pathogenesis of SjD.

Methods

Histological analysis, RNA-sequencing and flow cytometry were conducted on glands, lungs, eyes and lymphoid tissues of mice with regulatory T cell-specific deletion of stromal interaction proteins (STIM) 1 and 2 ( Stim1/2 Foxp3 ), which play key roles in calcium signaling and T cell function. The pathogenicity of T cells from Stim1/2 Foxp3 mice was investigated through adoptively transfer into lymphopenic host mice. Additionally, single-cell transcriptomic analysis was performed on peripheral blood mononuclear cells (PBMCs) of patients with SjD and control subjects.

Results

Stim1/2 Foxp3 mice develop a severe SjD-like disorder including salivary gland (SG) and lacrimal gland (LG) inflammation and dysfunction, autoantibodies and extraglandular symptoms. SG inflammation in Stim1/2 Foxp3 mice is characterized by T and B cell infiltration, and transcriptionally by a Th1 immune response that correlates strongly with the dysregulation observed in patients with SjD. Adoptive transfer of effector T cells from Stim1/2 Foxp3 mice demonstrates that the SjD-like disease is driven by interferon (IFN)-γ producing autoreactive CD4 + T cells independently of B cells and autoantiboodies. scRNA-seq analysis identifies increased Th1 responses and attenuated memory Treg function in PBMCs of patients with SjD.

Conclusions

We report a more accurate mouse model of SjD while providing evidence for a critical role of Treg cells and IFN-γ producing Th1 cells in the pathogenesis of SjD, which may be effective targets for therapy.

Tissue-infiltrating alloreactive T cells require Id3 to deflect PD-1-mediated immune suppression during GVHD

ABSTRACT

Persisting alloreactive donor T cells in target tissues are a determinant of graft-versus-host disease (GVHD), but the transcriptional regulators that control the persistence and function of tissue-infiltrating T cells remain elusive. We demonstrate here that Id3, a DNA-binding inhibitor, is critical for sustaining T-cell responses in GVHD target tissues in mice, including the liver and intestine. Id3 loss results in aberrantly expressed PD-1 in polyfunctional T helper 1 (Th1) cells, decreased tissue-infiltrating PD-1+ polyfunctional Th1 cell numbers, impaired maintenance of liver TCF-1+ progenitor-like T cells, and inhibition of GVHD. PD-1 blockade restores the capacity of Id3-ablated donor T cells to mediate GVHD. Single-cell RNA-sequencing analysis revealed that Id3 loss leads to significantly decreased CD28- and PI3K/AKT-signaling activity in tissue-infiltrating polyfunctional Th1 cells, an indicator of active PD-1/PD-L1 effects. Id3 is also required for protecting CD8+ T cells from the PD-1 pathway-mediated suppression during GVHD. Genome-wide RNA-sequencing analysis reveals that Id3 represses transcription factors (e.g., Nfatc2, Fos, Jun, Ets1, and Prdm1) that are critical for PD-1 transcription, exuberant effector differentiation, and interferon responses and dysfunction of activated T cells. Id3 achieves these effects by restraining the chromatin accessibility for these transcription factors. Id3 ablation in donor T cells preserved their graft vs tumor effects in mice undergoing allogeneic hematopoietic stem cell transplantation. Furthermore, CRISPR/Cas9 knockout of ID3 in human CD19-directed chimeric antigen receptor T cells retained their antitumor activity in NOD/SCID/IL2Rg-/- mice early after administration. These findings identify that ID3 is an important target to reduce GVHD, and the gene-editing program of ID3 may have broad implications in T-cell-based immunotherapy.

TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders

Transforming growth factor (TGF)-β1, a member of the TGF-β superfamily, is produced by many immune and nonimmune cells and has pleiotropic effects on both innate and adaptive immunity, especially in the control of T-cell differentiation and function. Consistently, loss of TGF-β1 function is associated with exacerbated T-cell-dependent inflammatory responses that culminate in pathological processes in allergic and immune-mediated diseases. In this review, we highlight the roles of TGF-β1 in immunity, focusing mainly on its ability to promote differentiation of regulatory T cells, T helper (Th)-17, and Th9 cells, thus contributing to amplifying or restricting T-cell responses in health and human diseases (e.g., inflammatory bowel diseases, type 1 diabetes, asthma, and MS). In addition, we discuss the involvement of Smad7, an inhibitor of TGF-β1 signaling, in immune-mediated disorders (e.g., psoriasis, rheumatoid arthritis, MS, and inflammatory bowel diseases), as well as the discordant results of clinical trials with mongersen, an oral pharmaceutical compound containing a Smad7 antisense oligonucleotide, in patients with Crohn's disease. Further work is needed to ascertain the reasons for such a discrepancy as well as to identify better candidates for treatment with Smad7 inhibitors.

TGF-β uncouples glycolysis and inflammation in macrophages and controls survival during sepsis

Changes in metabolism of macrophages are required to sustain macrophage activation in response to different stimuli. We showed that the cytokine TGF-β (transforming growth factor-β) regulates glycolysis in macrophages independently of inflammatory cytokine production and affects survival in mouse models of sepsis. During macrophage activation, TGF-β increased the expression and activity of the glycolytic enzyme PFKL (phosphofructokinase-1 liver type) and promoted glycolysis but suppressed the production of proinflammatory cytokines. The increase in glycolysis was mediated by an mTOR-c-MYC-dependent pathway, whereas the inhibition of cytokine production was due to activation of the transcriptional coactivator SMAD3 and suppression of the activity of the proinflammatory transcription factors AP-1, NF-κB, and STAT1. In mice with LPS-induced endotoxemia and experimentally induced sepsis, the TGF-β-induced enhancement in macrophage glycolysis led to decreased survival, which was associated with increased blood coagulation. Analysis of septic patient cohorts revealed that the expression of PFKL, TGFBRI (which encodes a TGF-β receptor), and F13A1 (which encodes a coagulation factor) in myeloid cells positively correlated with COVID-19 disease. Thus, these results suggest that TGF-β is a critical regulator of macrophage metabolism and could be a therapeutic target in patients with sepsis.

A role of Achaete-scute complex homolog 2 in T follicular regulatory cell development

T follicular regulatory (Tfr) cells, a subset of CD4⁺ Foxp3⁺ regulatory T (Treg) cells, locate to the lymphoid follicle and germinal center (GC) and regulate antibody responses. Tfr cells express the functional molecules of follicular helper T (Tfh) cells, including CXCR5 and Bcl6. CD25^- mature Tfr cells differentiate from CD25⁺ Treg cells through CD25⁺ immature Tfr cells. Others and we have shown that Achaete-scute complex homolog 2 (Ascl2) plays a role in Tfh cell development; however, the role of Ascl2 in the development of Tfr cells remains unclear. Here, we found that Ascl2 was highly and preferentially expressed in CD25⁺ Tfr cells and CD25^- Tfr cells, and that the differentiation from CD25⁺ Tfr cells to CD25^- Tfr cells was impaired by the absence of Ascl2. Furthermore, the forced Ascl2 expression in Treg cells downregulated CD25 expression and suppressed IL-2-induced phosphorylation of STAT5, which is known to suppress CD25^- Tfr cell development. Finally, we found that the downregulation of CD25 by Ascl2 in Treg cells is independent of Bach2, which also regulates CD25 downregulation in CD25⁺ Tfr cells. These results suggest that Ascl2 plays a vital role in developing Tfr cells, possibly by downregulating CD25 expression in a Bach2-independent mechanism.

Id4 modulates salivary gland homeostasis and its expression is downregulated in IgG4-related disease via miR-486-5p

Salivary glands are physiologically orchestrated by the coordinated balance between cell differentiation, proliferation, apoptosis, and interactions between epithelial, mesenchymal endothelial, and neuronal cells, and they are frequent sites of manifestations of Sjögren's syndrome (SS) or IgG4-related disease (IgG4-RD). However, little is known about salivary gland homeostasis and its involvement in those diseases. Inhibitor of DNA binding/differentiation 4 (Id4) is an Id protein involved in the transcriptional control of many biological events, including differentiation. Studies of Id4-deficient mice revealed that Id4-deficient submandibular glands were smaller and exhibited accelerated differentiation, compared with those from wild-type littermates. In addition, dry mouth symptoms and Th17 expansion in splenocytes were also observed in the absence of Id4. Furthermore, Id4 levels in the salivary glands of patients with IgG4-RD, but not SS, were significantly decreased compared with those of healthy controls. miRNA-mRNA integrated analysis demonstrated that miR-486-5p was upregulated in IgG4-RD patients and that it might regulate Id4 in the lesion sites. Together, these results provide evidence for the inhibitory role of Id4 in salivary differentiation, and a critical association between Id4 downregulation and IgG4-RD.

Biology and clinical relevance of follicular cytotoxic T cells

Follicular cytotoxic T (Tfc) cells are a newly identified subset of CD8⁺ T cells enriched in B cell follicles and their surroundings, which integrate multiple functions such as killing, memory, supporting and regulation. Tfc cells share similarities with follicular helper T (Tfh) cells, conventional cytotoxic CD8⁺ T (Tc cells)cells and follicular regulatory T (Tfr) cells, while they express distinct transcription factors, phenotype, and perform different functions. With the participation of cytokines and cell-cell interactions, Tfc cells modulate Tfh cells and B cells and play an essential role in regulating the humoral immunity. Furthermore, Tfc cells have been found to change in their frequencies and functions during the occurrence and progression of chronic infections, immune-mediated diseases and cancers. Strategies targeting Tfc cells are under investigations, bringing novel insights into control of these diseases. We summarize the characteristics of Tfc cells, and introduce the roles and potential targeting modalities of Tfc cells in different diseases.

Semaphorin 6D-expressing mesenchymal cells regulate IL-10 production by ILC2s in the lung

Group 2 innate lymphoid cells (ILC2s) have features specific to the niches in which they reside, and we found that semaphorin 6D signaling in the lung niche controls IL-10 production by ILC2s.

Group 2 innate lymphoid cells (ILC2s) have been implicated in both physiologic tissue remodeling and allergic pathology, yet the niche signaling required for ILC2 properties is poorly understood. Here, we show that an axonal guidance cue semaphorin 6D (Sema6D) plays critical roles in the maintenance of IL-10–producing ILC2s. Sema6d^−/− mice exhibit a severe steady-state reduction in ILC2s in peripheral sites such as the lung, visceral adipose tissue, and mesentery. Interestingly, loss of Sema6D results in suppressed alarmin-driven type 2 cytokine production but increased IL-10 production by lung ILC2s both in vitro and in vivo. Consequently, Sema6d^−/− mice are resistant to the development of allergic lung inflammation. We further found that lung mesenchymal cells highly express Sema6D, and that niche-derived Sema6D is responsible for these phenotypes through plexin A1. Collectively, these findings suggest that niche-derived Sema6D is implicated in physiological and pathological characteristics of ILC2s.

Immunoregulatory signal networks and tumor immune evasion mechanisms: insights into therapeutic targets and agents in clinical development

Through activation of immune cells, the immune system is responsible for identifying and destroying infected or otherwise damaged cells including tumorigenic cells that can be recognized as foreign, thus maintaining homeostasis. However, tumor cells have evolved several mechanisms to avoid immune cell detection and killing, resulting in tumor growth and progression. In the tumor microenvironment, tumor infiltrating immune cells are inactivated by soluble factors or tumor promoting conditions and lose their effects on tumor cells. Analysis of signaling and crosstalk between immune cells and tumor cells have helped us to understand in more detail the mechanisms of tumor immune evasion and this forms basis for drug development strategies in the area of cancer immunotherapy. In this review, we will summarize the dominant signaling networks involved in immune escape and describe the status of development of therapeutic strategies to target tumor immune evasion mechanisms with focus on how the tumor microenvironment interacts with T cells.

Opposing functions of circadian protein DBP and atypical E2F family E2F8 in anti-tumor Th9 cell differentiation

Interleukin-9 (IL-9)-producing CD4⁺ T helper cells (Th9) have been implicated in allergy/asthma and anti-tumor immunity, yet molecular insights on their differentiation from activated T cells, driven by IL-4 and transforming growth factor-beta (TGF-β), is still lacking. Here we show opposing functions of two transcription factors, D-binding protein (DBP) and E2F8, in controlling Th9 differentiation. Specifically, TGF-β and IL-4 signaling induces phosphorylation of the serine 213 site in the linker region of the Smad3 (pSmad3L-Ser²¹³) via phosphorylated p38, which is necessary and sufficient for Il9 gene transcription. We identify DBP and E2F8 as an activator and repressor, respectively, for Il9 transcription by pSmad3L-Ser²¹³. Notably, Th9 cells with siRNA-mediated knockdown for Dbp or E2f8 promote and suppress tumor growth, respectively, in mouse tumor models. Importantly, DBP and E2F8 also exhibit opposing functions in regulating human TH9 differentiation in vitro. Thus, our data uncover a molecular mechanism of Smad3 linker region-mediated, opposing functions of DBP and E2F8 in Th9 differentiation.

Signaling networks controlling ID and E protein activity in T cell differentiation and function

E and inhibitor of DNA binding (ID) proteins are involved in various cellular developmental processes and effector activities in T cells. Recent findings indicate that E and ID proteins are not only responsible for regulating thymic T cell development but also modulate the differentiation, function, and fate of peripheral T cells in multiple immune compartments. Based on the well-established E and ID protein axis (E-ID axis), it has been recognized that ID proteins interfere with the dimerization of E proteins, thus restricting their transcriptional activities. Given this close molecular relationship, the extent of expression or stability of these two protein families can dynamically affect the expression of specific target genes involved in multiple aspects of T cell biology. Therefore, it is essential to understand the endogenous proteins or extrinsic signaling pathways that can influence the dynamics of the E-ID axis in a cell-specific and context-dependent manner. Here, we provide an overview of E and ID proteins and the functional outcomes of the E-ID axis in the activation and function of multiple peripheral T cell subsets, including effector and memory T cell populations. Further, we review the mechanisms by which endogenous proteins and signaling pathways alter the E-ID axis in various T cell subsets influencing T cell function and fate at steady-state and in pathological settings. A comprehensive understanding of the functions of E and ID proteins in T cell biology can be instrumental in T cell-specific targeting of the E-ID axis to develop novel therapeutic modalities in the context of autoimmunity and cancer.

Shifting gears: Id3 enables recruitment of E proteins to new targets during T cell development and differentiation

Shifting levels of E proteins and Id factors are pivotal in T cell commitment and differentiation, both in the thymus and in the periphery. Id2 and Id3 are two different factors that prevent E proteins from binding to their target gene cis-regulatory sequences and inducing gene expression. Although they use the same mechanism to suppress E protein activity, Id2 and Id3 play very different roles in T cell development and CD4 T cell differentiation. Id2 imposes an irreversible choice in early T cell precursors between innate and adaptive lineages, which can be thought of as a railway switch that directs T cells down one path or another. By contrast, Id3 acts in a transient fashion downstream of extracellular signals such as T cell receptor (TCR) signaling. TCR-dependent Id3 upregulation results in the dislodging of E proteins from their target sites while chromatin remodeling occurs. After the cessation of Id3 expression, E proteins can reassemble in the context of a new genomic landscape and molecular context that allows induction of different E protein target genes. To describe this mode of action, we have developed the “Clutch” model of differentiation. In this model, Id3 upregulation in response to TCR signaling acts as a clutch that stops E protein activity (“clutch in”) long enough to allow shifting of the genomic landscape into a different “gear”, resulting in accessibility to different E protein target genes once Id3 decreases (“clutch out”) and E proteins can form new complexes on the DNA. While TCR signal strength and cytokine signaling play a role in both peripheral and thymic lineage decisions, the remodeling of chromatin and E protein target genes appears to be more heavily influenced by the cytokine milieu in the periphery, whereas the outcome of Id3 activity during T cell development in the thymus appears to depend more on the TCR signal strength. Thus, while the Clutch model applies to both CD4 T cell differentiation and T cell developmental transitions within the thymus, changes in chromatin accessibility are modulated by biased inputs in these different environments. New emerging technologies should enable a better understanding of the molecular events that happen during these transitions, and how they fit into the gene regulatory networks that drive T cell development and differentiation.

Id3 expression identifies CD4+ memory Th1 cells

Memory CD4⁺ T cells play a pivotal role in mediating long-term protective immunity, positioning them as an important target in vaccine development. However, multiple functionally distinct helper CD4⁺ T-cell subsets can arise in response to a single invading pathogen, complicating the identification of rare populations of memory precursor cells during the effector phase of infection and memory CD4⁺ T cells following pathogen clearance and the contraction phase of infection. Furthermore, current literature remains unclear regarding whether a single CD4⁺ memory T-cell lineage gives rise to secondary CD4⁺ T helper subsets or if there are unique memory precursor cells within each helper lineage. A majority of T follicular helper (Tfh) cells, which have established memory potential, express Id3, an inhibitor of E protein transcription factors, following acute viral infection. We show that expression of Id3 definitively identified a subset of cells within both the CD4⁺ Tfh and T helper 1 (Th1) lineages at memory time points that exhibited memory potential, with the capacity for significant re-expansion in response to secondary infection. Notably, we demonstrate that a subset of Th1 cells that survive into the memory phase were marked by Id3 expression and possessed the potential for enhanced expansion and generation of both Th1 and Tfh secondary effector cell populations in a secondary response to pathogen. Additionally, these cells exhibited enrichment of key molecules associated with memory potential when compared with Id3^lo Th1 cells. Therefore, we propose that Id3 expression serves as an important marker to indicate multipotent potential in memory CD4⁺ T cells.

The E-Id Axis Instructs Adaptive Versus Innate Lineage Cell Fate Choice and Instructs Regulatory T Cell Differentiation

Immune responses are primarily mediated by adaptive and innate immune cells. Adaptive immune cells, such as T and B cells, evoke antigen-specific responses through the recognition of specific antigens. This antigen-specific recognition relies on the V(D)J recombination of immunoglobulin (Ig) and T cell receptor (TCR) genes mediated by recombination-activating gene (Rag)1 and Rag2 (Rag1/2). In addition, T and B cells employ cell type-specific developmental pathways during their activation processes, and the regulation of these processes is strictly regulated by the transcription factor network. Among these factors, members of the basic helix-loop-helix (bHLH) transcription factor mammalian E protein family, including E12, E47, E2-2, and HEB, orchestrate multiple adaptive immune cell development, while their antagonists, Id proteins (Id1-4), function as negative regulators. It is well established that a majority of T and B cell developmental trajectories are regulated by the transcriptional balance between E and Id proteins (the E-Id axis). E2A is critically required not only for B cell but also for T cell lineage commitment, whereas Id2 and Id3 enforce the maintenance of naïve T cells and naïve regulatory T (Treg) cells. Here, we review the current knowledge of E- and Id-protein function in T cell lineage commitment and Treg cell differentiation.

A systematic comparison of FOSL1, FOSL2 and BATF-mediated transcriptional regulation during early human Th17 differentiation

Th17 cells are essential for protection against extracellular pathogens, but their aberrant activity can cause autoimmunity. Molecular mechanisms that dictate Th17 cell-differentiation have been extensively studied using mouse models. However, species-specific differences underscore the need to validate these findings in human. Here, we characterized the human-specific roles of three AP-1 transcription factors, FOSL1, FOSL2 and BATF, during early stages of Th17 differentiation. Our results demonstrate that FOSL1 and FOSL2 co-repress Th17 fate-specification, whereas BATF promotes the Th17 lineage. Strikingly, FOSL1 was found to play different roles in human and mouse. Genome-wide binding analysis indicated that FOSL1, FOSL2 and BATF share occupancy over regulatory regions of genes involved in Th17 lineage commitment. These AP-1 factors also share their protein interacting partners, which suggests mechanisms for their functional interplay. Our study further reveals that the genomic binding sites of FOSL1, FOSL2 and BATF harbour hundreds of autoimmune disease-linked SNPs. We show that many of these SNPs alter the ability of these transcription factors to bind DNA. Our findings thus provide critical insights into AP-1-mediated regulation of human Th17-fate and associated pathologies.

Functional Analysis of the Transcriptional Regulator IκB-ζ in Intestinal Homeostasis

BACKGROUND

The Toll-like receptor signaling pathway contributes to the regulation of intestinal homeostasis through interactions with commensal bacteria. Although the transcriptional regulator IκB-ζ can be induced by Toll-like receptor signaling, its role in intestinal homeostasis is still unclear.

AIMS

To investigate the role of IκB-ζ in gut homeostasis.

METHODS

DSS-administration induced colitis in control and IκB-ζ-deficient mice. The level of immunoglobulins in feces was detected by ELISA. The immunological population in lamina propria (LP) was analyzed by FACS.

RESULTS

IκB-ζ-deficient mice showed severe inflammatory diseases with DSS administration in the gut. The level of IgM in the feces after DSS administration was less in IκB-ζ-deficient mice compared to control mice. Upon administration of DSS, IκB-ζ-deficient mice showed exaggerated intestinal inflammation (more IFN-g-producing CD4⁺ T cells in LP), and antibiotic treatment canceled this inflammatory phenotype.

CONCLUSION

IκB-ζ plays a crucial role in maintaining homeostasis in the gut.

Hypermethylation at the CXCR5 gene locus limits trafficking potential of CD8+ T cells into B-cell follicles during HIV-1 infection

CD8+ T-cells play an important role in HIV control. However, in human lymph nodes (LNs), only a small subset of CD8+ T-cells expresses CXCR5, the chemokine receptor required for cell migration into B cell follicles, which are major sanctuaries for HIV persistence in individuals on therapy. Here, we investigate the impact of HIV infection on follicular CD8+ T-cells (fCD8s) frequencies, trafficking pattern and CXCR5 regulation. We show that, although HIV infection results in a marginal increase of fCD8s in LN, the majority of HIV-specific CD8+ T-cells are CXCR5 negative (non-fCD8s) (p<0.003). Mechanistic investigations using ATAC-seq showed that non-fCD8s have closed chromatin at the CXCR5 transcriptional start site (TSS). DNA bisulfite sequencing identified DNA hypermethylation at the CXCR5 TSS as the most probable cause of closed chromatin. Transcriptional factor footprints analysis revealed enrichment of transforming growth factors (TGFs) at the TSS of fCD8s. In-vitro stimulation of non-fCD8s with recombinant TGF-β resulted in significant increase in CXCR5 expression (fCD8s). Thus, this study identifies TGF-β signaling as a viable strategy for increasing fCD8s frequencies in follicular areas of the LN where they are needed to eliminate HIV infected cells, with implications for HIV cure strategies.

FOXP3 variants are independently associated with transforming growth factor Β1 plasma levels in female patients with inflammatory bowel disease

OBJECTIVE

The aim of this study was to evaluate the association of -924 G>A (rs2232365) and -3279 C>A (rs3761548) FOXP3 variants with IBD susceptibility, clinical and endoscopic activity, and IL-10 and TGF-β1 plasma levels.

METHOD

The study included 110 IBD female patients, 60 with Ulcerative Colitis (UC) and 50 with Crohn's Disease (CD), and 154 female controls. FOXP3 variants were determined with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). Plasma levels of IL-10 and TGF-β1 were determined using immunofluorimetric assay.

RESULTS

AA genotype of rs2232365 and rs3761548 was associated with CD (OR = 3.147, 95% CI 1.015-9.758, p = 0.047) and UC (OR = 3.221, 95% CI 1.050-9.876, p = 0.041) susceptibility, respectively. However, were not associated with TGF-β1 and IL-10 levels, and endoscopic/clinical activity disease. GAGA haplotype was associated with IBD (OR = 4.003, 95% CI 1.100-14.56, p = 0.035) and UC susceptibility (OR = 6.107, 95% CI 1.609-23.18, p = 0.008). In addition, IBD patients with the GAGA haplotype had lower TGF-β1 levels (p = 0.041). Moreover, G/C haplotype (dominant model) had a protective effect of 60% in CD susceptibility and lower Endoscopic Severity Index.

CONCLUSIONS

These results suggest that FOXP3 variants could exert a role in the Treg, which could be one of the factors involved in the susceptibility and pathogenesis of IBD.

The Pathogenic Roles of IL-22 in Colitis: Its Transcription Regulation by Musculin in T Helper Subsets and Innate Lymphoid Cells

IL-22 plays a crucial role in promoting inflammation, antimicrobial immunity and tissue repair at barrier surfaces. The role of IL-22 in colitis is still controversial: while IL-22 has a protective effect on gut epithelium in acute injuries, it also enhances colitis in a context-dependent manner. Here, we summarize the Yin and Yang of IL-22 in colitis. Particularly, we emphasize the role of innate lymphoid cells (ILCs) in IL-22 production and regulation. A previously underappreciated transcription factor, Musculin (MSC), has been recently identified to be expressed in not only Th17 cells, but also RORγt+/Id2+ IL-22-producing group 3 ILCs in the gut of naïve mice. We hypothesize that the co-expression and interaction of MSC with the key transcription repressor Id2 in developing lymphoid cells (e.g., in LTi cells) and ILC precursors might fine tune the developmental programs or regulate the plasticity of adaptive Th subset and innate ILCs. The much-elevated expression of IL-22 in MSC-/- ILC3s suggests that MSC may function as: 1) a transcription suppressor for cytokines, particularly for IL-22, and/or 2) a gatekeeper for specific lineages of Th cells and innate ILCs as well. Amelioration of colitis symptoms in MSC-/- mice by IL-22-blocking agent IL-22BP-Fc suggests a counterintuitive pathogenic role of IL-22 in the absence of MSC as a checkpoint. The theory that exuberant production of IL-22 under pathological conditions (e.g., in human inflammatory bowel disease, IBD) may cause epithelial inflammation due to endoplasmic reticulum (ER) stress response is worth further investigation. Rheostatic regulation of IL-22 may be of therapeutic value to restore homeostatic balance and promote intestinal health in human colitis.

Up-regulated DNA-binding inhibitor Id3 promotes differentiation of regulatory T cell to influence antiviral immunity in chronic hepatitis B virus infection

AIM

Elevated Treg is relevant to persistent HBV infection, and the regulatory mechanism of Treg levels remains unclear. E proteins are important transcriptional regulators and could be antagonized by inhibitors of DNA-binding (Id) 1-4. We aim to clarify the role of Ids during HBV infection.

MAIN METHODS

Changes of Ids and their relationship with Treg were investigated in both HBV transfection model and hepatitis B patients. Significance of Ids was studied by in vitro Treg differentiation induction with Id inhibited or over-expressed. The role of inflammatory cytokines for Id was studied by co-culture. RNA-Seq was conducted to explore the differentially expressed genes in Id-overexpressed CD4 T cells upon Treg differentiation induction conditions.

KEY FINDINGS

Id-overexpressed mice attenuated virus clearance in HBV transfection model. In the HBV transfection mouse model, Tregs were up-regulated, with Id3 increased in Treg as well. Clinically, circulating Tregs in chronic hepatitis B (CHB) patients were elevated, and elevated Id3 transcriptional levels were positively correlated with Tregs. IL-1β could up-regulate Id3 in Treg cells induced in vitro. RNA-Seq revealed that increased Id could cause a series of signaling pathway changes during Treg differentiation.

SIGNIFICANCE

Id3 is elevated during HBV infection to ease Treg differentiation, and the antiviral immunity is influenced that make the infection to develop into chronic state.

Searching for the Elusive Regulatory Innate Lymphoid Cell

The complex nature of the innate lymphoid cell (ILC) family and wide range of ILC effector functions has been the focus of intense research. In addition to important roles in host defense, ILCs have central roles in maintaining tissue homeostasis and can promote immune tolerance. Alterations within the microenvironment can impart new functions on ILCs, and can even induce conversion to a distinct ILC family member. Complicating current definitions of ILCs are recent findings of distinct regulatory ILC populations that limit inflammatory responses or recruit other immunosuppressive cells such as regulatory T cells. Whether these populations are distinct ILC family members or rather canonical ILCs that exhibit immunoregulatory functions due to microenvironment signals has been the subject of much debate. In this review, we highlight studies identifying regulatory populations of ILCs that span regulatory NK-like cells, regulatory ILCs, and IL-10-producing ILC2s.

Profound Treg perturbations correlate with COVID-19 severity

Regulatory T cells (Tregs) are responsible for restraining excessive inflammation, a hallmark of COVID-19. We identified a striking phenotype in Tregs from patients with severe disease, as well as an interesting role for interleukin (IL)-6 and IL-18. An increased suppressive profile, including increased Treg proportions, combined with the expression of proinflammatory mediators, distinguished severe patients and persisted in some of those recovered. This phenotype is in notable similarity to that found in tumor-infiltrating Tregs, which are generally associated with poor prognosis, and suggests both a detrimental role for these cells in COVID-19 as well as a potential explanation for some of the still largely unexplored complications associated with recovery.

The hallmark of severe COVID-19 is an uncontrolled inflammatory response, resulting from poorly understood immunological dysfunction. We hypothesized that perturbations in FoxP3⁺ T regulatory cells (Treg), key enforcers of immune homeostasis, contribute to COVID-19 pathology. Cytometric and transcriptomic profiling revealed a distinct Treg phenotype in severe COVID-19 patients, with an increase in Treg proportions and intracellular levels of the lineage-defining transcription factor FoxP3, correlating with poor outcomes. These Tregs showed a distinct transcriptional signature, with overexpression of several suppressive effectors, but also proinflammatory molecules like interleukin (IL)-32, and a striking similarity to tumor-infiltrating Tregs that suppress antitumor responses. Most marked during acute severe disease, these traits persisted somewhat in convalescent patients. A screen for candidate agents revealed that IL-6 and IL-18 may individually contribute different facets of these COVID-19–linked perturbations. These results suggest that Tregs may play nefarious roles in COVID-19, by suppressing antiviral T cell responses during the severe phase of the disease, and by a direct proinflammatory role.

RNA sequencing of blood in coronary artery disease: involvement of regulatory T cell imbalance

BACKGROUND

Cardiovascular disease had a global prevalence of 523 million cases and 18.6 million deaths in 2019. The current standard for diagnosing coronary artery disease (CAD) is coronary angiography. Surprisingly, despite well-established clinical indications, up to 40% of the one million invasive cardiac catheterizations return a result of 'no blockage'. The present studies employed RNA sequencing of whole blood to identify an RNA signature in patients with angiographically confirmed CAD.

METHODS

Whole blood RNA was depleted of ribosomal RNA (rRNA) and analyzed by single-molecule sequencing of RNA (RNAseq) to identify transcripts associated with CAD (TRACs) in a discovery group of 96 patients presenting for elective coronary catheterization. The resulting transcript counts were compared between groups to identify differentially expressed genes (DEGs).

RESULTS

Surprisingly, 98% of DEGs/TRACs were down-regulated ~ 1.7-fold in patients with mild to severe CAD (> 20% stenosis). The TRACs were independent of comorbid risk factors for CAD, such as sex, hypertension, and smoking. Bioinformatic analysis identified an enrichment in transcripts such as FoxP1, ICOSLG, IKZF4/Eos, SMYD3, TRIM28, and TCF3/E2A that are likely markers of regulatory T cells (Treg), consistent with known reductions in Tregs in CAD. A validation cohort of 80 patients confirmed the overall pattern (92% down-regulation) and supported many of the Treg-related changes. TRACs were enriched for transcripts associated with stress granules, which sequester RNAs, and ciliary and synaptic transcripts, possibly consistent with changes in the immune synapse of developing T cells.

CONCLUSIONS

These studies identify a novel mRNA signature of a Treg-like defect in CAD patients and provides a blueprint for a diagnostic test for CAD. The pattern of changes is consistent with stress-related changes in the maturation of T and Treg cells, possibly due to changes in the immune synapse.

Ubiquitin Specific Protease 1 Expression and Function in T Cell Immunity

T cells are essential mediators of immune responses against infectious diseases and provide long-lived protection from reinfection. The differentiation of naive to effector T cells and the subsequent differentiation and persistence of memory T cell populations in response to infection is a highly regulated process. E protein transcription factors and their inhibitors, Id proteins, are important regulators of both CD4⁺ and CD8⁺ T cell responses; however, their regulation at the protein level has not been explored. Recently, the deubiquitinase USP1 was shown to stabilize Id2 and modulate cellular differentiation in osteosarcomas. In this study, we investigated a role for Usp1 in posttranslational control of Id2 and Id3 in murine T cells. We show that Usp1 was upregulated in T cells following activation in vitro or following infection in vivo, and the extent of Usp1 expression correlated with the degree of T cell expansion. Usp1 directly interacted with Id2 and Id3 following T cell activation. However, Usp1 deficiency did not impact Id protein abundance in effector T cells or alter effector T cell expansion or differentiation following a primary infection. Usp1 deficiency resulted in a gradual loss of memory CD8⁺ T cells over time and reduced Id2 protein levels and proliferation of effector CD8⁺ T cell following reinfection. Together, these results identify Usp1 as a player in modulating recall responses at the protein level and highlight differences in regulation of T cell responses between primary and subsequent infection encounters. Finally, our observations reveal differential regulation of Id2/3 proteins between immune versus nonimmune cell types.

IL-10-Producing ILCs: Molecular Mechanisms and Disease Relevance

Innate lymphoid cells (ILCs) are mainly composed of natural killer (NK) cells and helper-like lymphoid cells, which play a vital role in maintaining tissue homeostasis, enhancing adaptive immunity and regulating tissue inflammation. Alteration of the distribution and function of ILCs subgroups are closely related to the pathogenesis of inflammatory diseases and cancers. Interleukin-10 (IL-10) is a highly pleiotropic cytokine, and can be secreted by several cell types, among of which ILCs are recently verified to be a key source of IL-10. So far, the stable production of IL-10 can only be observed in certain NK subsets and ILC2s. Though the regulatory mechanisms for ILCs to produce IL-10 are pivotal for understanding ILCs and potential intervenes of diseases, which however is largely unknown yet. The published studies show that ILCs do not share exactly the same mechanisms for IL-10 production with helper T cells. In this review, the molecular mechanisms regulating IL-10 production in NK cells and ILC2s are discussed in details for the first time, and the role of IL-10-producing ILCs in diseases such as infections, allergies, and cancers are summarized.

Haplotypes of FOXP3 genetic variants are associated with susceptibility, autoantibodies, and TGF-β1 in patients with systemic lupus erythematosus

The aim of this study was to evaluate the association of rs2232365 (-924 G > A) and rs3761548 (-3279 C > A) FOXP3 variants with systemic lupus erythematosus (SLE) susceptibility, TGF-β1 plasma levels, autoantibodies, and LN nephritis, and SLE disease activity index (SLEDAI). The study included 196 SLE female patients and 157 female controls. FOXP3 variants were determined with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Plasma levels of TGF-β1 were determined using immunofluorimetric assay. The AA genotype [OR: 2.650, CI 95%(1.070-6.564), p = 0.035] and A allele [OR: 2.644, CI 95%(1.104-6.333), p = 0.029] were associated with SLE diagnosis in the -3279 C > A. The A/A haplotype was associated with SLE [OR: 3.729, CI 95%(1.006-13.820), p = 0.049]. GCGC haplotype patients had higher TGF-β1 levels (p = 0.012) than other haplotypes. Patients with -924 AA genotype showed higher frequency of anti-dsDNA (p = 0.012) and anti-U1RNP (p = 0.036). The A/C haplotype had higher SLEDAI score [OR: 1.119, CI 95%(1.015-1.234), p = 0.024] and ACAC haplotype higher frequency of anti-dsDNA [OR: 3.026, CI 95%(1.062-8.624), p = 0.038], anti-U1RNP [OR: 5.649, CI 95%(1.199-26.610), p = 0.029] and nephritis [OR: 2.501, CI 95%(1.004-6.229), p = 0.049]. Our data demonstrate that the G/C haplotype provides protection for SLE. While the presence of allele A of both variants could favor autoimmunity, disease activity, and LN.

Profound Treg perturbations correlate with COVID-19 severity

The hallmark of severe COVID-19 disease has been an uncontrolled inflammatory response, resulting from poorly understood immunological dysfunction. We explored the hypothesis that perturbations in FoxP3+ T regulatory cells (Treg), key enforcers of immune homeostasis, contribute to COVID-19 pathology. Cytometric and transcriptomic profiling revealed a distinct Treg phenotype in severe COVID-19 patients, with an increase in both Treg proportions and intracellular levels of the lineage-defining transcription factor FoxP3, which correlated with poor outcomes. Accordingly, these Tregs over-expressed a range of suppressive effectors, but also pro-inflammatory molecules like IL32. Most strikingly, they acquired similarity to tumor-infiltrating Tregs, known to suppress local anti-tumor responses. These traits were most marked in acute patients with severe disease, but persisted somewhat in convalescent patients. These results suggest that Tregs may play nefarious roles in COVID-19, via suppressing anti-viral T cell responses during the severe phase of the disease, and/or via a direct pro-inflammatory role.

Inactivation of endothelial ZEB1 impedes tumor progression and sensitizes tumors to conventional therapies

Current antiangiogenic therapy is limited by its cytostatic property, scarce drug delivery to the tumor, and side toxicity. To address these limitations, we unveiled the role of ZEB1, a tumor endothelium-enriched zinc-finger transcription factor, during tumor progression. We discovered that the patients who had lung adenocarcinomas with high ZEB1 expression in tumor endothelium had increased prevalence of metastases and markedly reduced overall survival after the diagnosis of lung cancer. Endothelial ZEB1 deletion in tumor-bearing mice diminished tumor angiogenesis while eliciting persistent tumor vascular normalization by epigenetically repressing TGF-β signaling. This consequently led to improved blood and oxygen perfusion, enhanced chemotherapy delivery and immune effector cell infiltration, and reduced tumor growth and metastasis. Moreover, targeting vascular ZEB1 remarkably potentiated the anticancer activity of nontoxic low-dose cisplatin. Treatment with low-dose anti-programmed cell death protein 1 (anti-PD-1) antibody elicited tumor regression and markedly extended survival in ZEB1-deleted mice, conferring long-term protective anticancer immunity. Collectively, we demonstrated that inactivation of endothelial ZEB1 may offer alternative opportunities for cancer therapy with minimal side effects. Targeting endothelium-derived ZEB1 in combination with conventional chemotherapy or immune checkpoint blockade therapy may yield a potent and superior anticancer effect.

Transcriptional regulation of Treg homeostasis and functional specification

CD4+Foxp3+ regulatory T (Treg) cells are key players in keeping excessive inflammation in check. Mounting evidence has shown that Treg cells exert much more diverse functions in both immunological and non-immunological processes. The development, maintenance and functional specification of Treg cells are regulated by multilayered factors, including antigens and TCR signaling, cytokines, epigenetic modifiers and transcription factors (TFs). In the review, we will focus on TFs by summarizing their unique and redundant roles in Treg cells under physiological and pathophysiological conditions. We will also discuss the recent advances of Treg trajectories between lymphoid organs and non-lymphoid tissues. This review will provide an updated view of the newly identified TFs and new functions of known TFs in Treg biology.

Interaction between γδTCR signaling and the E protein-Id axis in γδ T cell development

γδ T cells acquire their functional properties in the thymus, enabling them to exert rapid innate-like responses. To understand how distinct γδ T cell subsets are generated, we have developed a Two-Stage model for γδ T cell development. This model is predicated on the finding that γδTCR signal strength impacts E protein activity through graded upregulation of Id3. Our model proposes that cells enter Stage 1 in response to a γδTCR signaling event in the cortex that activates a γδ T cell-specific gene network. Part of this program includes the upregulation of chemokine receptors that guide them to the medulla. In the medulla, Stage 1 cells receive distinct combinations of γδTCR, cytokine, and/co-stimulatory signals that induce their transit into Stage 2, either toward the γδT1 or the γδT17 lineage. The intersection between γδTCR and cytokine signals can tune Id3 expression, leading to different outcomes even in the presence of strong γδTCR signals. The thymic signaling niches required for γδT17 development are segregated in time and space, providing transient windows of opportunity during ontogeny. Understanding the regulatory context in which E proteins operate at different stages will be key in defining how their activity levels impose functional outcomes.

Correlation of the levels of DNA-binding inhibitor Id3 and regulatory T cells with SLE disease severity

E proteins, a subset of basic helix-loop-helix (bHLH) proteins, are transcription activators and their functions are inhibited by DNA-binding inhibitor (Id) 1-4. Studies have shown that Treg levels are decreased in Id3 knockout mice. Mice over-expressing Id1 in CD4 T cells possessed a greater number of regulatory T cells (Treg) and exhibited attenuated experimental autoimmune encephalomyelitis (EAE). The significance of Id proteins in human systemic lupus erythematosus (SLE) remains unclear. In this study, we systematically analyzed Id transcription in naïve, memory CD4 cells and regulatory T cells in peripheral blood mononuclear cells (PBMCs) in patients with active or inactive SLE. In parallel, Treg subsets in PBMCs were analyzed using different strategies. Id expression levels were correlated with Treg numbers as well as clinical indicators. We found that Id genes expressed in human peripheral CD4 cells were mainly Id2 and Id3. Id3 levels were significantly elevated in CD4⁺CD25^hi T cells of patients with active SLE. Likewise, Id3 levels were positively correlated with increased CD4⁺FoxP3⁺ and CD4⁺Helios⁺FoxP3⁺ Treg cells in these patients. Id3 levels were found to be positively correlated with erythrocyte sedimentation rate (ESR), lupus anticoagulant (LAC), ribosomal antibody and SLE Disease Activity Index (SLEDAI) in patients with active SLE. Mice overexpressing Id1 in CD4⁺ T cells possessed significantly higher Treg levels in spleen and lower autoantibody concentrations in serum. Our results suggest that during the pathogenesis of SLE, up-regulation of Id3 can promote Treg differentiation to play an inhibitory effect on autoimmune responses.

Th9 Cell Differentiation and Its Dual Effects in Tumor Development

With the improved understanding of the molecular pathogenesis and characteristics of cancers, the critical role of the immune system in preventing tumor development has been widely accepted. The understanding of the relationship between the immune system and cancer progression is constantly evolving, from the cancer immunosurveillance hypothesis to immunoediting theory and the delicate balance in the tumor microenvironment. Currently, immunotherapy is regarded as a promising strategy against cancers. Although adoptive cell therapy (ACT) has shown some exciting results regarding the rejection of tumors, the effect is not always satisfactory. Cellular therapy with CD4⁺ T cells remains to be further explored since the current ACT is mainly focused on CD8⁺ cytotoxic T lymphocytes (CTLs). Recently, Th9 cells, a subgroup of CD4⁺ T helper cells characterized by the secretion of IL-9 and IL-10, have been reported to be effective in the elimination of solid tumors and to exhibit superior antitumor properties to Th1 and Th17 cells. In this review, we summarize the most recent advances in the understanding of Th9 cell differentiation and the dual role, both anti-tumor and pro-tumor effects, of Th9 cells in tumor progression.

Comprehensive analysis of circRNA expression profiles and circRNA-associated competing endogenous RNA networks in the development of mouse thymus

The thymus plays an irreplaceable role as a primary lymphoid organ. However, the complicate processes of its development and involution are incompletely understood. Accumulating evidence indicates that non-coding RNAs play key roles in the regulation of biological development. At present, the studies of the circRNA profiles and of circRNA-associated competing endogenous RNAs (ceRNAs) in the thymus are still scarce. Here, deep-RNA sequencing was used to study the biological mechanisms underlying the development process (from 2-week-old to 6-week-old) and the recession process (from 6-week-old to 3-month-old) of the mouse thymus. It was found that 196 circRNAs, 233 miRNAs and 3807 mRNAs were significantly dysregulated. The circRNA-associated ceRNA networks were constructed in the mouse thymus, which were mainly involved in early embryonic development and the proliferation and division of T cells. Taken together, these results elucidated the regulatory roles of ceRNAs in the development and involution processes of the mouse thymus.

TAGAP instructs Th17 differentiation by bridging Dectin activation to EPHB2 signaling in innate antifungal response

The TAGAP gene locus has been linked to several infectious diseases or autoimmune diseases, including candidemia and multiple sclerosis. While previous studies have described a role of TAGAP in T cells, much less is known about its function in other cell types. Here we report that TAGAP is required for Dectin-induced anti-fungal signaling and proinflammatory cytokine production in myeloid cells. Following stimulation with Dectin ligands, TAGAP is phosphorylated by EPHB2 at tyrosine 310, which bridges proximal Dectin-induced EPHB2 activity to downstream CARD9-mediated signaling pathways. During Candida albicans infection, mice lacking TAGAP mount defective immune responses, impaired Th17 cell differentiation, and higher fungal burden. Similarly, in experimental autoimmune encephalomyelitis model of multiple sclerosis, TAGAP deficient mice develop significantly attenuated disease. In summary, we report that TAGAP plays an important role in linking Dectin-induced signaling to the promotion of effective T helper cell immune responses, during both anti-fungal host defense and autoimmunity.

TAGAP gene variants are linked to human autoimmunity. Here the authors identify TAGAP as a Dectin-1 and EphB2-binding protein mediating antifungal innate immune signaling and cytokine production, and demonstrate TAGAP in non-T cells promotes Th17 response in mouse models of infection and autoimmunity.

Wheat Bran Intake Enhances the Secretion of Bacteria-Binding IgA in a Lumen of the Intestinal Tract by Incrementing Short Chain Fatty Acid Production Through Modulation of Gut Microbiota

Wheat bran, a by-product generated in large amounts during wheat processing, consists of 36.5% to 52.4% total dietary fiber. In this study, we investigated the effects of wheat bran intake on the intestinal tract immune system through the modulation of gut microbiota. Balb/c mice were fed with AIN-93G diets containing wheat bran with 2 different particle sizes (average particle size of 53 µm: powdered wheat bran; PWB, and 350 µm: granulated wheat bran; WB) as dietary fibers for 4 weeks. In the wheat bran intake groups, short chain fatty acids (SCFAs: acetic acid, propionic acid, and butyric acid) in the feces were increased after the intake of both particle-size diets, especially in the PWB group, in which the increase occurred immediately. 16S rRNA-based metagenomics of the fecal microbiota revealed that the Shannon Index (α-diversity) and weighted UniFrac distances (β-diversity) in wheat bran intake groups were significantly higher than those in the Control group, and the ratio of the certain family within the order Clostridiales in the fecal microbiota was increased after wheat bran intake, probably some including SCFA-producing bacteria. CXCR5, which is a key surface marker expressed on T follicular helper (Tfh) cells, tended to increase at the expression level in wheat bran intake groups. In addition, the amounts of secretory immunoglobulin A (IgA) and the proportion of IgA-binding bacteria in the feces from wheat bran intake groups were significantly higher than those from the Control group. These findings suggest that wheat bran may enhance Tfh-mediated IgA production in the intestine by SCFA increment through the modulation of gut microbiota and is expected to maintain and improve a healthy intestinal environment.

Depletion of ID3 enhances mesenchymal stem cells therapy by targeting BMP4 in Sjögren's syndrome

Mesenchymal stem cell (MSCs) transplantation has been used to treat Sjögren’s syndrome (SS) based on the immunoregulatory properties of MSCs. However, the effectiveness need improving and its underlying intrinsic mechanisms remain largely unknown. Here, we show that Id3 is upregulated in bone marrow-derived MSCs (BMMSCs) isolated from NOD/ShiLtJ mice, a widely used SS model, compared with ICR mice as control, suggesting that it functions in SS development and therapy. Transplantation of Id3-deficient BMMSCs rescues salivary gland function more effective than wild-type BMMSCs in NOD/ShiLtJ mice. Mechanistically, we show that ID3 negatively regulated BMP4 expression by preventing binding of basic helix–loop–helix protein E2A to the promoter of the Bmp4 gene. BMP4 in turn promoted PGE2 production in MSCs, and exhibited enhanced suppressive activities of T-cell proliferation and Th1 differentiation. Importantly, BMMSCs from SS patients showed significantly lower BMP4 and PGE2 expression than those from healthy individuals. Taken together, our findings revealed the targeting Id3 may be therapeutically useful for improving MSC immunoregulation and effectiveness of MSCs therapy for SS.

Analytical Characterization of an Enzyme-Linked Immunosorbent Assay for the Measurement of Transforming Growth Factor β1 in Human Plasma

Background

The transforming growth factor β (TGF-β)–signaling pathway has emerged as a promising therapeutic target for many disease states including hepatocellular carcinoma (HCC). Because of the pleiotropic effects of this pathway, patient selection and monitoring may be important. TGF-β1 is the most prevalent isoform, and an assay to measure plasma levels of TGF-β1 would provide a rational biomarker to assist with patient selection. Therefore, the objective of this study was to analytically validate a colorimetric ELISA for the quantification of TGF-β1 in human plasma.

Methods

A colorimetric sandwich ELISA for TGF-β1 was analytically validated per Clinical and Laboratory Standards Institute protocols by assessment of precision, linearity, interfering substances, and stability. A reference range for plasma TGF-β1 was established for apparently healthy individuals and potential applicability was demonstrated in HCC patients.

Results

Precision was assessed for samples ranging from 633 to 10822 pg/mL, with total variance ranging from 28.4% to 7.2%. The assay was linear across the entire measuring range, and no interference of common blood components or similar molecules was observed. For apparently healthy individuals, the average TGF-β1 level was 1985 ± 1488 pg/mL compared to 4243 ± 2003 pg/mL for HCC patients. Additionally, the TGF-β1 level in plasma samples was demonstrated to be stable across all conditions tested, including multiple freeze–thaw cycles.

Conclusions

The ELISA described in this report is suitable for the quantification of TGF-β1 in human plasma and for investigational use in an approved clinical study.

Induction of Follicular-Like CXCR5+ CD8+ T Cells by TGF-β1/IL-23 Is Limited During HIV Infection

Follicular CD4⁺ T cells are the main HIV reservoirs due to, among other factors, the low frequency of CD8⁺ T cells in lymphoid follicles. Follicular CXCR5⁺ CD8⁺ T cells are associated with HIV control, but their differentiation conditions are yet undefined. In this study, we explored the in vitro effect of transforming growth factor (TGF)-β1, interleukin (IL)-12, and IL-23 on the induction of CXCR5, the follicle homing receptor, in human circulating CD8⁺ T cells from seronegative, and treated HIV-infected individuals. The combination of TGF-β1 plus IL-23 induced the highest expression of CXCR5 in purified CD8⁺ T cells. These CXCR5⁺ CD8⁺ T cells also expressed a transcriptional and phenotypic profile similar to that of follicular CD4⁺ T cells, such as the upregulation of BCL6, inducible costimulator and CD40L, and downregulation of PRDM1. These cells responded in vitro to CXCL13 and had low expression of CCR7. In addition, after polyclonal stimulation, they produced IL-21, interferon-γ, and de novo perforin. However, in comparison with seronegative individuals, CD8⁺ T cells from HIV-infected patients had a lower response to TGF-β1/IL-23, a defect that was restored with the blockade of the programmed cell death 1 inhibitory receptor. Thus, TGF-β1 plus IL-23 induce follicular-like CXCR5⁺ CD8⁺ T cells in seronegative individuals, but in HIV-infected patients there is a limited response which could impair the generation of this cell population.

Blocking Triggering Receptor Expressed on Myeloid Cells-1-Positive Tumor-Associated Macrophages Induced by Hypoxia Reverses Immunosuppression and Anti-Programmed Cell Death Ligand 1 Resistance in Liver Cancer

Tumor-associated macrophages (TAMs) are recognized as antitumor suppressors, but how TAMs behave in the hypoxic environment of hepatocellular carcinoma (HCC) remains unclear. Here, we demonstrated that hypoxia inducible factor 1α induced increased expression of triggering receptor expressed on myeloid cells-1 (TREM-1) in TAMs, resulting in immunosuppression. Specifically, TREM-1-positive (TREM-1⁺ ) TAMs abundant at advanced stages of HCC progression indirectly impaired the cytotoxic functions of CD8⁺ T cells and induced CD8⁺ T-cells apoptosis. Biological and functional assays showed that TREM-1⁺ TAMs had higher expression of programmed cell death ligand 1 (PD-L1) under hypoxic environment. However, TREM-1⁺ TAMs could abrogate spontaneous and PD-L1-blockade-mediated antitumor effects in vivo, suggesting that TREM-1⁺ TAM-induced immunosuppression was dependent on a pathway separate from PD-L1/programmed cell death 1 axis. Moreover, TREM-1⁺ TAM-associated regulatory T cells (Tregs) were crucial for HCC resistance to anti-PD-L1 therapy. Mechanistically, TREM-1⁺ TAMs elevated chemokine (C-C motif) ligand 20 expression through the extracellular signal-regulated kinase/NF-κβ pathway in response to hypoxia and tumor metabolites leading to CCR6⁺ Foxp3⁺ Treg accumulation. Blocking the TREM-1 pathway could significantly inhibit tumor progression, reduce CCR6⁺ Foxp3⁺ Treg recruitment, and improve the therapeutic efficacy of PD-L1 blockade. Thus, these data demonstrated that CCR6⁺ Foxp3⁺ Treg recruitment was crucial for TREM-1⁺ TAM-mediated anti-PD-L1 resistance and immunosuppression in hypoxic tumor environment. Conclusion: This study highlighted that the hypoxic environment initiated the onset of tumor immunosuppression through TREM-1⁺ TAMs attracting CCR6⁺ Foxp3⁺ Tregs, and TREM-1⁺ TAMs endowed HCC with anti-PD-L1 therapy resistance.

The Transcriptional Regulator Id2 Is Critical for Adipose-Resident Regulatory T Cell Differentiation, Survival, and Function

Adipose regulatory T cells (aTregs) have emerged as critical cells for the control of local and systemic inflammation. In this study, we show a distinctive role for the transcriptional regulator Id2 in the differentiation, survival, and function of aTregs in mice. Id2 was highly expressed in aTregs compared with high Id3 expression in lymphoid regulatory T cells (Tregs). Treg-specific deletion of Id2 resulted in a substantial decrease in aTregs, whereas Tregs in the spleen and lymph nodes were unaffected. Additionally, loss of Id2 resulted in decreased expression of aTreg-associated markers, including ST2, CCR2, KLRG1, and GATA3. Gene expression analysis revealed that Id2 expression was essential for the survival of aTregs, and loss of Id2 increased cell death in aTregs due to increased Fas expression. Id2-mediated aTreg depletion resulted in increased systemic inflammation, increased inflammatory macrophages and CD8⁺ effector T cells, and loss of glucose tolerance under standard diet conditions. Thus, we reveal an unexpected and novel function for Id2 in mediating differentiation, survival, and function of aTregs that when lost result in increased metabolic perturbation.

Inhibitor of DNA binding in heart development and cardiovascular diseases

Id proteins, inhibitors of DNA binding, are transcription regulators containing a highly conserved helix-loop-helix domain. During multiple stages of normal cardiogenesis, Id proteins play major roles in early development and participate in the differentiation and proliferation of cardiac progenitor cells and mature cardiomyocytes. The fact that a depletion of Ids can cause a variety of defects in cardiac structure and conduction function is further evidence of their involvement in heart development. Multiple signalling pathways and growth factors are involved in the regulation of Ids in a cell- and tissue- specific manner to affect heart development. Recent studies have demonstrated that Ids are related to multiple aspects of cardiovascular diseases, including congenital structural, coronary heart disease, and arrhythmia. Although a growing body of research has elucidated the important role of Ids, no comprehensive review has previously compiled these scattered findings. Here, we introduce and summarize the roles of Id proteins in heart development, with the hope that this overview of key findings might shed light on the molecular basis of consequential cardiovascular diseases. Furthermore, we described the future prospective researches needed to enable advancement in the maintainance of the proliferative capacity of cardiomyocytes. Additionally, research focusing on increasing embryonic stem cell culture adaptability will help to improve the future therapeutic application of cardiac regeneration.

E-protein regulatory network links TCR signaling to effector Treg cell differentiation

T cell antigen receptor (TCR) signaling is essential for the differentiation and maintenance of effector regulatory T (Treg) cells. However, the contribution of individual TCR-dependent genes in Treg cells to the maintenance of immunotolerance remains largely unknown. Here we demonstrate that Treg cells lacking E protein undergo further differentiation into effector cells that exhibit high expression of effector Treg signature genes, including IRF4, ICOS, CD103, KLRG-1, and RORγt. E protein-deficient Treg cells displayed increased stability and enhanced suppressive capacity. Transcriptome and ChIP-seq analyses revealed that E protein directly regulates a large proportion of the genes that are specific to effector Treg cell activation, and importantly, most of the up-regulated genes in E protein-deficient Treg cells are also TCR dependent; this indicates that E proteins comprise a critical gene regulatory network that links TCR signaling to the control of effector Treg cell differentiation and function.

Innate Lymphoid Cell Development: A T Cell Perspective

Innate lymphoid cells (ILCs) and natural killer (NK) cells have garnered considerable interest due to their unique functional properties in immune defense and tissue homeostasis. Our current understanding of how these cells develop has been greatly facilitated by knowledge of T cell biology. Models of T cell differentiation provided the basis for a conceptual classification of these innate effectors and inspired a scheme of their activation and regulation. In this review, we discuss NK cell and ILC development from a "T cell standpoint" in an attempt to extend the analogy between adaptive T cells and their innate ILC and NK cell counterparts.

Features and roles of T helper 9 cells and interleukin 9 in immunological diseases

T helper 9 (T_H9) cells are considered as newly classified helper T cells that have an important role in the regulation of immune responses. Since these cells preferentially produce IL-9, these cells are termed T_H9 cells. Recently, the role of T_H9 and its signature cytokine (IL-9) has been investigated in a wide range of diseases, including autoimmunity, allergy, infections, cancer and immunodeficiency. Herein, we review the most recent data concerning T_H9 cells and IL-9 as well as their roles in disease. These insights suggest that T_H9 cells are a future target for therapeutic intervention.

ID2 and ID3 are indispensable for Th1 cell differentiation during influenza virus infection in mice

Antigen-specific Th1 cells could be a passage to the infection sites during infection to execute effector functions, such as help CD8⁺ T cells to localize in these sites by secretion of anti-viral cytokines-IFN-γ or direct cytotoxicity of antigen-bearing cells. However, the molecular components that modulate Th1 cell differentiation and function in response to viral infection remain incompletely understood. Here, we reported that both inhibitor of DNA binding 3(Id3) protein and inhibitor of DNA binding 2(Id2) protein promoted Th1 cell differentiation. Depletion of Id3 or Id2 led to severe defect of Th1 cell differentiation during influenza virus infection. Whereas depletion of both Id3 and Id2 in CD4⁺ T cells restrained Th1 cell differentiation to a greater extent, indicating that Id3 and Id2 nonredundantly regulate Th1 cell differentiation. Moreover, deletion of E-proteins, the antagonists of Id proteins, greatly enhanced Th1 cell differentiation. Mechanistic study indicated that E-proteins suppressed Th1 cell differentiation by directly binding to the regulatory elements of Th1 cell master regulator T-bet and regulate T-bet expression. Thus, our findings identified Id-protein's importance for Th1 cells and clarified the nonredundant role of Id3 and Id2 in regulating Th1 cell differentiation, providing novel insight that Id3-Id2-E protein axis are essential for Th1 cell polarization.

Inflammation-induced Id2 promotes plasticity in regulatory T cells

TH17 cells originating from regulatory T (Treg) cells upon loss of the Treg-specific transcription factor Foxp3 accumulate in sites of inflammation and aggravate autoimmune diseases. Whether an active mechanism drives the generation of these pathogenic 'ex-Foxp3 TH17' cells, remains unclear. Here we show that pro-inflammatory cytokines enhance the expression of transcription regulator Id2, which mediates cellular plasticity of Treg into ex-Foxp3 TH17 cells. Expression of Id2 in in vitro differentiated iTreg cells reduces the expression of Foxp3 by sequestration of the transcription activator E2A, leading to the induction of TH17-related cytokines. Treg-specific ectopic expression of Id2 in mice significantly reduces the Treg compartment and causes immune dysregulation. Cellular fate-mapping experiments reveal enhanced Treg plasticity compared to wild-type, resulting in exacerbated experimental autoimmune encephalomyelitis pathogenesis or enhanced anti-tumor immunity. Our findings suggest that controlling Id2 expression may provide a novel approach for effective Treg cell immunotherapies for both autoimmunity and cancer.

Comparative Analysis of Gene Expression Profiles of Human Dental Fluorosis and Kashin-Beck Disease

To explore the pathologies of Kashin-Beck disease (KBD) and KBD accompanied with dental fluorosis (DF), we conducted a comparative analysis of gene expression profiles. 12 subjects were recruited, including 4 KBD patients, 4 patients with KBD and DF and 4 healthy subjects. Genome-wide expression profiles from their peripheral blood mononuclear cells were evaluated by customized oligonucleotide microarray. R programming software was used for the microarray data analysis followed by functional enrichment analysis through KOBAS. Several potential biomarkers were identified, and quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) was used for their validation. In this study, 28 genes and 8 genes were found to be up- and down-regulated respectively in KBD patients compared with health subjects. In patients with KBD and DF, we obtained 10 up-regulated and 3 down-regulated genes compared with health controls. Strikingly, no differential expression gene (DEG) was identified between the two groups of patients. A total of 10 overlaps (DUSP2, KLRF1, SRP19, KLRC3, CD69, SIK1, ITGA4, ID3, HSPA1A, GPR18) were obtained between DEGs of patients with KBD and patients with KBD and DF. They play important roles in metabolism, differentiation, apoptosis and bone-development. The relative abundance of 8 DEGs, i.e. FCRL6, KLRC3, CXCR4, CD93, CLK1, GPR18, SRP19 and KLRF1, were further confirmed by qRT-PCR analysis.