Microbial ligand-independent regulation of lymphopoiesis by NOD1.

Aberrant differentiation of progenitor cells in the hematopoietic system is known to severely impact host immune responsiveness. Here we demonstrate that NOD1, a cytosolic innate sensor of bacterial peptidoglycan, also functions in murine hematopoietic cells as a major regulator of both the generation and differentiation of lymphoid progenitors as well as peripheral T lymphocyte homeostasis. We further show that NOD1 mediates these functions by facilitating STAT5 signaling downstream of hematopoietic cytokines. In steady-state, loss of NOD1 resulted in a modest but significant decrease in numbers of mature T, B and natural killer cells. During systemic protozoan infection this defect was markedly enhanced, leading to host mortality. Lack of functional NOD1 also impaired T cell-dependent anti-tumor immunity while preventing colitis. These findings reveal that, in addition to its classical role as a bacterial ligand receptor, NOD1 plays an important function in regulating adaptive immunity through interaction with a major host cytokine signaling pathway.

Interleukin-33-activated neuropeptide CGRP-producing memory Th2 cells cooperate with somatosensory neurons to induce conjunctival itch.

Allergic conjunctivitis is a chronic inflammatory disease that is characterized by severe itch in the conjunctiva, but how neuro-immune interactions shape the pathogenesis of severe itch remains unclear. We identified a subset of memory-type pathogenic Th2 cells that preferentially expressed Il1rl1-encoding ST2 and Calca-encoding calcitonin-gene-related peptide (CGRP) in the inflammatory conjunctiva using a single-cell analysis. The IL-33-ST2 axis in memory Th2 cells controlled the axonal elongation of the peripheral sensory C-fiber and the induction of severe itch. Pharmacological blockade and genetic deletion of CGRP signaling in vivo attenuated scratching behavior. The analysis of giant papillae from patients with severe allergic conjunctivitis revealed ectopic lymphoid structure formation with the accumulation of IL-33-producing epithelial cells and CGRP-producing pathogenic CD4+ T cells accompanied by peripheral nerve elongation. Thus, the IL-33-ST2-CGRP axis directs severe itch with neuro-reconstruction in the inflammatory conjunctiva and is a potential therapeutic target for severe itch in allergic conjunctivitis.

Thioredoxin-interacting protein is essential for memory T cell formation via the regulation of the redox metabolism.

CD4+ memory T cells are central to long-lasting protective immunity and are involved in shaping the pathophysiology of chronic inflammation. While metabolic reprogramming is critical for the generation of memory T cells, the mechanisms controlling the redox metabolism in memory T cell formation remain unclear. We found that reactive oxygen species (ROS) metabolism changed dramatically in T helper-2 (Th2) cells during the contraction phase in the process of memory T cell formation. Thioredoxin-interacting protein (Txnip), a regulator of oxidoreductase, regulated apoptosis by scavenging ROS via the nuclear factor erythroid 2-related factor 2 (Nrf2)-biliverdin reductase B (Blvrb) pathway. Txnip regulated the pathology of chronic airway inflammation in the lung by controlling the generation of allergen-specific pathogenic memory Th2 cells in vivo. Thus, the Txnip-Nrf2-Blvrb axis directs ROS metabolic reprogramming in Th2 cells and is a potential therapeutic target for intractable chronic inflammatory diseases.

Elevated Myl9 reflects the Myl9-containing microthrombi in SARS-CoV-2-induced lung exudative vasculitis and predicts COVID-19 severity.

The mortality of coronavirus disease 2019 (COVID-19) is strongly correlated with pulmonary vascular pathology accompanied by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-triggered immune dysregulation and aberrant activation of platelets. We combined histological analyses using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy analyses of the lungs from autopsy samples and single-cell RNA sequencing of peripheral blood mononuclear cells to investigate the pathogenesis of vasculitis and immunothrombosis in COVID-19. We found that SARS-CoV-2 accumulated in the pulmonary vessels, causing exudative vasculitis accompanied by the emergence of thrombospondin-1-expressing noncanonical monocytes and the formation of myosin light chain 9 (Myl9)-containing microthrombi in the lung of COVID-19 patients with fatal disease. The amount of plasma Myl9 in COVID-19 was correlated with the clinical severity, and measuring plasma Myl9 together with other markers allowed us to predict the severity of the disease more accurately. This study provides detailed insight into the pathogenesis of vasculitis and immunothrombosis, which may lead to optimal medical treatment for COVID-19.

Suppression of Type I Interferon Signaling in Myeloid Cells by Autoantibodies in Severe COVID-19 Patients.

PURPOSE: Auto-antibodies (auto-abs) to type I interferons (IFNs) have been identified in patients with life-threatening coronavirus disease 2019 (COVID-19), suggesting that the presence of auto-abs may be a risk factor for disease severity. We therefore investigated the mechanism underlying COVID-19 exacerbation induced by auto-abs to type I IFNs. METHODS: We evaluated plasma from 123 patients with COVID-19 to measure auto-abs to type I IFNs. We performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells from the patients with auto-abs and conducted epitope mapping of the auto-abs. RESULTS: Three of 19 severe and 4 of 42 critical COVID-19 patients had neutralizing auto-abs to type I IFNs. Patients with auto-abs to type I IFNs showed no characteristic clinical features. scRNA-seq from 38 patients with COVID-19 revealed that IFN signaling in conventional dendritic cells and canonical monocytes was attenuated, and SARS-CoV-2-specific BCR repertoires were decreased in patients with auto-abs. Furthermore, auto-abs to IFN-α2 from COVID-19 patients with auto-abs recognized characteristic epitopes of IFN-α2, which binds to the receptor. CONCLUSION: Auto-abs to type I IFN found in COVID-19 patients inhibited IFN signaling in dendritic cells and monocytes by blocking the binding of type I IFN to its receptor. The failure to properly induce production of an antibody to SARS-CoV-2 may be a causative factor of COVID-19 severity.

The transcription factor Sox4 is a downstream target of signaling by the cytokine TGF-ß and suppresses T(H)2 differentiation.

Sox4 is a transcription factor that regulates various developmental processes. Here we show that Sox4 was induced by TGF-ß and negatively regulated the transcription factor GATA-3, the master regulator of function of T helper type 2 (T(H)2) cells, by two distinct mechanisms. First, Sox4 bound directly to GATA-3, preventing its binding to GATA-3 consensus DNA sequences. Second, Sox4 bound to the promoter region of the gene encoding interleukin 5 (IL-5), a T(H)2 cytokine, and prevented binding of GATA-3 to this promoter. T(H)2 cell-driven airway inflammation was modulated by alterations in Sox4 expression. Thus, Sox4 acted as a downstream target of TGF-ß to inhibit GATA-3 function, T(H)2 differentiation and T(H)2 cell-mediated inflammation.

CD4+ T cells in inflammatory diseases: pathogenic T-helper cells and the CD69-Myl9 system.

CD4+ T cells not only direct immune responses against infectious micro-organisms but are also involved in the pathogenesis of inflammatory diseases. In the last two to three decades, various researchers have identified and characterized several functional CD4+ T-cell subsets, including T-helper 1 (Th1), Th2, Th9 and Th17 cells and regulatory T (Treg) cells. In this mini-review, we introduce the concept of pathogenic Th cells that induce inflammatory diseases with a model of disease induction by a population of pathogenic Th cells: the 'pathogenic Th population disease-induction model'. We will focus on Th2 cells that induce allergic airway inflammation-pathogenic Th2 cells (Tpath2 cells)-and discuss the nature of Tpath2 cells that shape the pathology of chronic inflammatory diseases. Various Tpath2-cell subsets have been identified and their unique features are summarized in mouse and human systems. Second, we will discuss how Th cells migrate and are maintained in chronic inflammatory lesions. We propose a model known as the 'CD69-Myl9 system'. CD69 is a cell surface molecule expressed on activated T cells and interaction with its ligand myosin light chain 9 (Myl9) is required for the induction of inflammatory diseases. Myl9 molecules in the small vessels of inflamed lungs may play a crucial role in the migration of activated T cells into inflammatory lesions. Emerging evidence may provide new insight into the pathogenesis of chronic inflammatory diseases and contribute to the development of new therapeutic strategies for intractable inflammatory disorders.

The polycomb protein Ezh2 regulates differentiation and plasticity of CD4(+) T helper type 1 and type 2 cells.

After antigen encounter by CD4(+) T cells, polarizing cytokines induce the expression of master regulators that control differentiation. Inactivation of the histone methyltransferase Ezh2 was found to specifically enhance T helper 1 (Th1) and Th2 cell differentiation and plasticity. Ezh2 directly bound and facilitated correct expression of Tbx21 and Gata3 in differentiating Th1 and Th2 cells, accompanied by substantial trimethylation at lysine 27 of histone 3 (H3K27me3). In addition, Ezh2 deficiency resulted in spontaneous generation of discrete IFN-γ and Th2 cytokine-producing populations in nonpolarizing cultures, and under these conditions IFN-γ expression was largely dependent on enhanced expression of the transcription factor Eomesodermin. In vivo, loss of Ezh2 caused increased pathology in a model of allergic asthma and resulted in progressive accumulation of memory phenotype Th2 cells. This study establishes a functional link between Ezh2 and transcriptional regulation of lineage-specifying genes in terminally differentiated CD4(+) T cells.

Eomesodermin controls interleukin-5 production in memory T helper 2 cells through inhibition of activity of the transcription factor GATA3.

The regulation of memory CD4(+) helper T (Th) cell function, such as polarized cytokine production, remains unclear. Here we show that memory T helper 2 (Th2) cells are divided into four subpopulations by CD62L and CXCR3 expression. All four subpopulations produced interleukin-4 (IL-4) and IL-13, whereas only the CD62L(lo)CXCR3(lo) population produced IL-5 accompanied by increased H3-K4 methylation at the Il5 gene locus. The transcription factor Eomesodermin (encoded by Eomes) was highly expressed in memory Th2 cells, whereas its expression was selectively downregulated in the IL-5-producing cells. Il5 expression was enhanced in Eomes-deficient cells, and Eomesodermin was shown to interact with the transcription factor GATA3, preventing GATA3 binding to the Il5 promoter. Memory Th2 cell-dependent airway inflammation was attenuated in the absence of the CD62L(lo)CXCR3(lo) population but was enhanced by Eomes-deficient memory Th2 cells. Thus, IL-5 production in memory Th2 cells is regulated by Eomesodermin via the inhibition of GATA3 activity.

Sensing of the microbiota by NOD1 in mesenchymal stromal cells regulates murine hematopoiesis.

The microbiota is known to influence the generation of hematopoietic progenitors, although the pathways underlying this process are still poorly understood. NOD1 and NOD2 are intracellular sensors for both Gram-positive and Gram-negative bacteria, but their role in steady-state hematopoiesis has never been characterized. We observed that stimulation with NOD1 or NOD2 ligand had no effect on the survival/proliferation of hematopoietic precursors. Nonetheless, NOD1, but not NOD2, ligand induced expression of multiple hematopoietic cytokines (interleukin-7 [IL-7], Flt3L, stem cell factor [SCF], ThPO, and IL-6) from bone marrow mesenchymal stromal cells (MSCs) in vitro. Moreover, in vivo administration of NOD1 ligand to germ-free mice restored the numbers of hematopoietic stem cells and precursors in bone marrow as well as serum concentrations of IL-7, Flt3L, SCF, and ThPO to the levels displayed by specific pathogen-free control animals. Based on these findings, we propose that NOD1 signaling in MSCs serves as an important pathway underlying the requirement for microbiota in the maintenance of steady-state hematopoiesis. This function is distinct from that triggered by lipopolysaccharide in both its broad effects on multiple progenitors and specific targeting of MSCs as cytokine producing intermediates.

Trithorax complex component Menin controls differentiation and maintenance of T helper 17 cells.

Epigenetic modifications, such as posttranslational modifications of histones, play an important role in gene expression and regulation. These modifications are in part mediated by the Trithorax group (TrxG) complex and the Polycomb group (PcG) complex, which activate and repress transcription, respectively. We herein investigate the role of Menin, a component of the TrxG complex in T helper (Th) cell differentiation and show a critical role for Menin in differentiation and maintenance of Th17 cells. Menin(-/-) T cells do not efficiently differentiate into Th17 cells, leaving Th1 and Th2 cell differentiation intact in in vitro cultures. Menin deficiency resulted in the attenuation of Th17-induced airway inflammation. In differentiating Th17 cells, Menin directly bound to the Il17a gene locus and was required for the deposition of permissive histone modifications and recruitment of the RNA polymerase II transcriptional complex. Interestingly, although Menin bound to the Rorc locus, Menin was dispensable for the induction of Rorc expression and permissive histone modifications in differentiating Th17 cells. In contrast, Menin was required to maintain expression of Rorc in differentiated Th17 cells, indicating that Menin is essential to stabilize expression of the Rorc gene. Thus, Menin orchestrates Th17 cell differentiation and function by regulating both the induction and maintenance of target gene expression.

Functionally distinct Gata3/Chd4 complexes coordinately establish T helper 2 (Th2) cell identity.

GATA binding protein 3 (Gata3) is a GATA family transcription factor that controls differentiation of naïve CD4 T cells into T helper 2 (Th2) cells. However, it is unknown how Gata3 simultaneously activates Th2-specific genes while repressing those of other Th lineages. Here we show that chromodomain helicase DNA-binding protein 4 (Chd4) forms a complex with Gata3 in Th2 cells that both activates Th2 cytokine transcription and represses the Th1 cytokine IFN-γ. We define a Gata3/Chd4/p300 transcriptional activation complex at the Th2 cytokine loci and a Gata3/Chd4-nucleosome remodeling histone deacetylase repression complex at the Tbx21 locus in Th2 cells. We also demonstrate a physiological role for Chd4 in Th2-dependent inflammation in an in vivo model of asthmatic inflammation. Thus, Gata3/Chd4 forms functionally distinct complexes, which mediate both positive and negative gene regulation to facilitate Th2 cell differentiation.

Paraoxonase-1 suppresses experimental colitis via the inhibition of IFN-γ production from CD4 T cells.

Crohn's disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract, where excessive Th1 cell responses are observed. We performed experiments to identify immunologically bioactive proteins in human plasma and found that paraoxonase (PON)-1, which has esterase activity and is associated with high-density lipoproteins, inhibited the IFN-γ production by both murine and human differentiating Th1 cells. Trinitrobenzene sulfonic acid-induced colitis was attenuated by the administration of PON-1. The beneficial effects of PON-1 were associated with a reduced ratio of IFN-γ-producing CD4 T cells in the mesenteric lymph nodes and decreased production of T cell-related cytokines in the colon. PON-1 inhibited the TCR-induced activation of ERK-MAPK signaling and the nuclear translocation of NF-κB in CD4 T cells. Interestingly, an excessive CD4 T cell response was observed in PON-1-deficient mice under physiological and pathological conditions. Additionally, the efficacy of PON-1 or G3C9-C284A (G3C9), which shows a higher esterase activity than PON-1, on colitis was similar to that of an anti-TNF-α mAb, which is a clinically used CD treatment. Moreover, G3C9 more effectively suppressed CD4(+)CD45RB(high) cell transfer-induced chronic colitis in mice than did PON-1, and the efficacy of G3C9 against the colitis was similar to that of the anti-TNF-α mAb. Therefore, PON-1 (or G3C9) administration may be clinically beneficial for CD patients.

Regulation of memory CD4 T-cell pool size and function by natural killer T cells in vivo.

To develop more effective vaccines and strategies to regulate chronic inflammatory diseases, it is important to understand the mechanisms of immunological memory. Factors regulating memory CD4(+) T helper (Th)-cell pool size and function remain unclear, however. We show that activation of type I invariant natural killer T (iNKT) cells with glycolipid ligands and activation of type II natural killer T (NKT) cells with the endogenous ligand sulfatide induced dramatic proliferation and expansion of memory, but not naïve, CD4 T cells. NKT cell-induced proliferation of memory Th1 and Th2 cells was dependent largely on the production of IL-2, with Th2-cell proliferation also affected by loss of IL-4. Type II NKT cells were also required for efficient maintenance of memory CD4 T cells in vivo. Activation of iNKT cells resulted in up-regulation of IFN-γ expression by memory Th2 cells. These IFN-γ-producing memory Th2 cells showed a decreased capability to induce Th2 cytokines and eosinophilic airway inflammation. Thus, activated NKT cells directly regulate memory CD4 T-cell pool size and function via the production of cytokines in vivo.

Type II membrane protein CD69 regulates the formation of resting T-helper memory.

Memory T-helper (Th) lymphocytes are crucial for the maintenance of acquired immunity to eliminate infectious pathogens. We have previously demonstrated that most memory Th lymphocytes reside and rest on stromal niches of the bone marrow (BM). Little is known, however, regarding the molecular basis for the generation and maintenance of BM memory Th lymphocytes. Here we show that CD69-deficient effector CD4 T lymphocytes fail to relocate into and persist in the BM and therefore to differentiate into memory cells. Consequently, CD69-deficient CD4 T cells fail to facilitate the production of high-affinity antibodies and the generation of BM long-lived plasma cells in the late phase of immune responses. Thus, CD69 is critical for the generation and maintenance of professional memory Th lymphocytes, which can efficiently help humoral immunity in the late phase. The deficit of immunological memory in CD69-deficient mice also highlights the essential role of BM for the establishment of Th memory.

Effect of invariant natural killer T cells with IL-5 and activated IL-6 receptor in ventilator-associated lung injury in mice.

Mechanical ventilation (MV) is well known to potentially cause ventilator-associated lung injury (VALI). It has also been reported recently that activation of invariant natural killer T (iNKT) cells is involved in the onset/progression of airway inflammation. We analyzed the roles of inflammatory cells, including iNKT cells, and cytokines/chemokines in a mouse model of VALI. C57BL/6 and Vα14(+)NKT cell-deficient (Jα18KO) female mice were subjected to MV for 5 hours. The MV induced lung injury in the mice, with severe histological abnormalities, elevation in the percentages of neutrophils in the bronchoalveolar lavage fluid (BALF), and increase in the number of iNKT cells in the lung. Jα18KO mice subjected to MV for 5 hours also showed lung injury, with decrease of the PaO2/FiO2 ratio (P/F ratio) and elevation of the levels of total protein, IL-5, IL-6, IL-12p40, and keratinocyte-derived cytokine (KC) in the BALF. Intranasal administration of anti-IL-5 monoclonal antibody (mAb) or anti-IL-6 receptor (IL-6R) mAb into the Jα18KO mice prior to the start of MV resulted in significant improvement in the blood oxygenation. In addition, the anti-IL-5 mAb administration was associated with a decrease in the levels of IL-5, IL-9, and IL-6R in the BALF, and anti-IL-6R mAb administration suppressed the mRNA expressions of IL-5, IL-6, IL-6R, and KC. These results suggest that iNKT cells may play a role in attenuating the inflammatory caused by ventilation through IL-5 and IL-6R.

Amphiregulin-producing TH2 cells facilitate esophageal fibrosis of eosinophilic esophagitis.

Background: Massive eosinophil infiltration into the esophagus is associated with subepithelial fibrosis and esophageal stricture in patients with eosinophilic esophagitis (EoE). However, the pathogenesis of esophageal fibrosis remains unclear. Objective: We sought to elucidate the cellular and molecular mechanisms underlying the induction of esophageal fibrosis. Methods: We established a murine model of EoE accompanied by fibrotic responses following long-term intranasal administration of house dust mite antigen. Using this murine model, we investigated the characteristics of immune cells infiltrating the fibrotic region of the inflamed esophagus using flow cytometry and histological analyses. We also analyzed the local inflammatory sites in the esophagus of patients with EoE using single-cell RNA sequencing, flow cytometry, and immunohistochemistry. Results: Enhanced infiltration of both amphiregulin-producing and IL-5-producing TH2 cells was detected in the fibrotic area of the esophagus in mice subjected to repeated house dust mite exposure. Deletion of amphiregulin in CD4+ T cells ameliorates esophageal fibrosis. An analysis of human esophageal biopsy samples showed that the infiltration of amphiregulin-producing CD4+ T cells was higher in patients with EoE than in control patients. Furthermore, the number of infiltrated amphiregulin-producing CD4+ T cells was associated with the degree of esophageal fibrosis in patients with EoE. Conclusions: Amphiregulin, produced by TH2 cells, contributes to esophageal fibrosis in EoE and may be a therapeutic target.

Correlation of interleukin-6 and monocyte chemotactic protein-1 concentrations with crescent formation and myeloperoxidase-specific anti-neutrophil cytoplasmic antibody titer in SCG/Kj mice by treatment with anti-interleukin-6 receptor antibody or mizoribine.

Myeloperoxidase-specific anti-neutrophil cytoplasmic antibody (MPO-ANCA) is associated with rapidly progressive glomerulonephritis (RPGN) and glomerular crescent formation. Pathogenic factors in RPGN were analyzed by using SCG/Kj mice, which spontaneously develop MPO-ANCA-associated RPGN. The serum concentration of soluble IL-6R was determined by using ELISA and those of another 23 cytokines and chemokines by Bio-Plex analysis. Sections of frozen kidney tissue were examined by fluorescence microscopy and the CD3(+) B220(+) T cell subset in the spleen determined by a flow cytometry. Concentrations of IL-6 and monocyte chemotactic protein-1 were significantly correlated with the percentages of crescent formation. Anti-IL-6R antibody, which has been effective in patients with rheumatoid arthritis, was administered to SCG/Kj mice to elucidate the role of IL-6 in the development of RPGN. MPO-ANCA titers decreased after administration of anti-IL-6R antibody, but not titers of mizoribine, which is effective in Kawasaki disease model mice. These results suggest that IL-6-mediated signaling is involved in the production of MPO-ANCA.

Apolipoprotein A-II suppressed concanavalin A-induced hepatitis via the inhibition of CD4 T cell function.

Con A-induced hepatitis has been used as a model of human autoimmune or viral hepatitis. During the process of identifying immunologically bioactive proteins in human plasma, we found that apolipoprotein A-II (ApoA-II), the second major apolipoprotein of high-density lipoprotein, inhibited the production of IFN-γ by Con A-stimulated mouse and human CD4 T cells. Con A-induced hepatitis was attenuated by the administration of ApoA-II. The beneficial effect of ApoA-II was associated with reduced leukocyte infiltration and decreased production of T cell-related cytokines and chemokines in the liver. ApoA-II inhibited the Con A-induced activation of ERK-MAPK and nuclear translocation of NFAT in CD4 T cells. Interestingly, exacerbated hepatitis was observed in ApoA-II-deficient mice, indicating that ApoA-II plays a suppressive role in Con A-induced hepatitis under physiological conditions. Moreover, the administration of ApoA-II after the onset of Con A-induced hepatitis was sufficient to suppress disease. Thus, the therapeutic effect of ApoA-II could be useful for patients with CD4 T cell-related autoimmune and viral hepatitis.