IL-9 and its receptor are predominantly involved in the pathogenesis of UC

Synovial IL-9 facilitates neutrophil survival, function and differentiation of Th17 cells in rheumatoid arthritis

Background

Role of Th9 cells and interleukin-9 (IL-9) in human autoimmune diseases such as psoriasis and ulcerative colitis has been explored only very recently. However, their involvement in human rheumatoid arthritis (RA) is not conclusive. Pathogenesis of RA is complex and involves various T cell subsets and neutrophils. Here, we aimed at understanding the impact of IL-9 on infiltrating immune cells and their eventual role in synovial inflammation in RA.

Methods

In vitro stimulation of T cells was performed by engagement of anti-CD3 and anti-CD28 monoclonal antibodies. Flow cytometry was employed for measuring intracellular cytokine, RORγt in T cells, evaluating apoptosis of neutrophils. ELISA was used for measuring soluble cytokine, Western blot analysis and confocal microscopy were used for STAT3 phosphorylation and nuclear translocation.

Results

We demonstrated synovial enrichment of Th9 cells and their positive correlation with disease activity (DAS28-ESR) in RA. Synovial IL-9 prolonged the survival of neutrophils, increased their matrix metalloprotienase-9 production and facilitated Th17 cell differentiation evidenced by induction of transcription factor RORγt and STAT3 phosphorylation. IL-9 also augmented the function of IFN-γ + and TNF-α + synovial T cells.

Conclusions

We provide evidences for critical role of IL-9 in disease pathogenesis and propose that targeting IL-9 may be an effective strategy to ameliorate synovial inflammation in RA. Inhibiting IL-9 may have wider impact on the production of pathogenic cytokines involved in autoimmune diseases including RA and may offer better control over the disease.

Electronic supplementary material

The online version of this article (10.1186/s13075-017-1505-8) contains supplementary material, which is available to authorized users.

JAK inhibition as a therapeutic strategy for immune and inflammatory diseases

This corrects the article DOI: 10.1038/nrd.2017.201.

JAK inhibition as a therapeutic strategy for immune and inflammatory diseases

The discovery of cytokines as key drivers of immune-mediated diseases has spurred efforts to target their associated signalling pathways. Janus kinases (JAKs) are essential signalling mediators downstream of many pro-inflammatory cytokines, and small-molecule inhibitors of JAKs (jakinibs) have gained traction as safe and efficacious options for the treatment of inflammation-driven pathologies such as rheumatoid arthritis, psoriasis and inflammatory bowel disease. Building on the clinical success of first-generation jakinibs, second-generation compounds that claim to be more selective are currently undergoing development and proceeding to clinical trials. However, important questions remain about the advantages and limitations of improved JAK selectivity, optimal routes and dosing regimens and how best to identify patients who will benefit from jakinibs. This Review discusses the biology of jakinibs from a translational perspective, focusing on recent insights from clinical trials, the development of novel agents and the use of jakinibs in a spectrum of immune and inflammatory diseases.

IL-36γ signaling controls the induced regulatory T cell-Th9 cell balance via NFκB activation and STAT transcription factors

Regulatory and effector T helper (Th) cells are abundant at mucosal surfaces, especially in the intestine, where they control the critical balance between tolerance and inflammation. However, the key factors that reciprocally dictate differentiation along these specific lineages remain incompletely understood. Here we report that the interleukin-1 (IL-1) family member IL-36γ signals through IL-36 receptor, myeloid differentiation primary response gene 88, and nuclear factor-κBp50 in CD4⁺ T cells to potently inhibit Foxp3-expressing induced regulatory T cell (T_reg) development, while concomitantly promoting the differentiation of Th9 cells via a IL-2-STAT5- (signal transducer and activator of transcription factor 5) and IL-4-STAT6-dependent pathway. Consistent with these findings, mice deficient in IL-36γ were protected from Th cell-driven intestinal inflammation and exhibited increased colonic T_reg cells and diminished Th9 cells. Our findings thus reveal a fundamental contribution for the IL-36/IL-36R axis in regulating the T_reg-Th9 cell balance with broad implications for Th cell-mediated disorders, such as inflammatory bowel diseases and particularly ulcerative colitis.

Heterogeneity of Human CD4(+) T Cells Against Microbes

CD4(+) T helper (Th) cells play a central role in the adaptive immune response by providing help to B cells and cytotoxic T cells and by releasing different types of cytokines in tissues to mediate protection against a wide range of pathogenic microorganisms. These functions are performed by different types of Th cells endowed with distinct migratory capacities and effector functions. Here we discuss how studies of the human T cell response to microbes have advanced our understanding of Th cell functional heterogeneity, in particular with the discovery of a distinct Th1 subset involved in the response to Mycobacteria and the characterization of two types of Th17 cells specific for extracellular bacteria or fungi. We also review new approaches to dissect at the clonal level the human CD4(+) T cell response induced by pathogens or vaccines that have revealed an unexpected degree of intraclonal diversification and propose a progressive and selective model of CD4(+) T cell differentiation.

The Immunogenicity of Branded and Biosimilar Infliximab in Rheumatoid Arthritis According to Th9-Related Responses

Our objective was to evaluate the immunogenicity of branded and biosimilar infliximab by detecting changes in T-helper-9 (Th9) percentages induced by an in vitro stimulation test.

METHODS

Peripheral blood mononuclear cells collected from 55 consecutive rheumatoid arthritis (RA) outpatients (15 drug free, 20 successfully treated with branded infliximab, 20 branded infliximab inadequate responders) and 10 healthy controls were cultured, with or without 50 μg/mL of infliximab originator (Remicade^®) or 50 μg/mL of infliximab biosimilar (Remsima^®) for 18 h. Th9 lymphocytes were identified by means of flow cytometry as PU.1 and IRF4-expressing, IL-9-secreting CD4⁺ T cells. Furthermore, the markers CCR7 and CD45RA were used to distinguish naïve from memory IL-9 producer cells.

RESULTS

Under unstimulated conditions, the drug-free RA patients had the highest percentages of Th9 lymphocytes. Following stimulation with branded infliximab, the percentages of PU.1 and IRF4-expressing Th9 cells, CCR7⁺, CD45RA^- (central memory) and CCR7^-, CD45RA^- (effector memory) cells significantly increased in the group of inadequate responders, but no significant variation was observed after exposure to the biosimilar of infliximab.

CONCLUSIONS

Th9 cells seem to be involved in the immune response to the epitopes of branded, but not biosimilar, infliximab, and this may depend on the recall and stimulation of both central and effector memory cells.

Serum Interleukin 9 Levels Predict Disease Severity and the Clinical Efficacy of Infliximab in Patients with Crohn's Disease

BACKGROUND

Interleukin (IL)-9 drives gut inflammation, but its role in Crohn's disease (CD) is unclear. We aimed to analyze correlations between serum IL-9 levels and disease severity and to evaluate their predictive value in relation to the clinical efficacy of infliximab (IFX) in patients with CD.

METHODS

Between January 2013 and December 2015, 100 consecutive patients with active CD and 50 age- and sex-matched control individuals were recruited from a tertiary center. Their serum IL-9 levels were measured using an enzyme-linked immunosorbent assay. Correlations between the serum IL-9 levels and disease severity were examined. The serum IL-9 level was explored as a predictor of clinical remission and mucosal healing at week 30 in 50 patients for whom IFX therapy was administered.

RESULTS

The serum IL-9 levels were significantly higher in the patients with active CD (22.0 pg/mL) than in the control individuals (6.3 pg/mL) (P < 0.001); they differed according to disease severity (moderate-to-severe CD: 29.1 pg/mL versus mild CD: 12.9 pg/mL) (P < 0.001), and they correlated well with the clinical activity of CD. IFX lowered the serum IL-9 level in patients who achieved efficacy at week 30. The areas under the curves for the IL-9 levels at weeks 14 and 30 that could predict clinical remission and mucosal healing at week 30 were 0.803 and 0.752 and 0.746 and 0.781, respectively.

CONCLUSIONS

Serum IL-9 levels correlate with disease severity and the clinical efficacy of IFX in patients with CD, and IL-9 may be a promising novel biomarker for CD monitoring.

S100A4 contributes to colitis development by increasing the adherence of Citrobacter rodentium in intestinal epithelial cells

S100A4 has been implicated in cancer and several inflammatory diseases, but its role in inflammatory bowel disease has not been well investigated. Here, upon infection with Citrobacter rodentium, a model for enteropathogenic Escherichia coli infection in humans, induced the infiltration of a large number of S100A4⁺ cells into the colon in wild type (WT) mice. Deficiency of S100A4 reduced weight loss, bacterial colonization and colonic pathology. Furthermore, the expression of inflammatory cytokines and the recruitment of macrophages and neutrophils also decreased significantly in S100A4 knock out (S100A4 ^-/-) mice. In vitro, soluble S100A4 directly up-regulated expression of integrin β-1 in intestinal epithelial cells and significantly increased the adherence of C. rodentium to intestinal epithelial cells. Additionally, the effects of S100A4 on the adherence of C. rodentium to epithelial cells could be abolished by a receptor for advanced glycation end products (RAGE)-specific inhibitor (FPS-ZM1). Therefore, these data indicate a novel mechanism for S100A4 that promotes colitis development by enhancing host adhesion and colonization of Citrobacter rodentium through the S100A4-mediated host inflammatory responses.

Selective degradation of PU.1 during autophagy represses the differentiation and antitumour activity of TH9 cells

Autophagy, a catabolic mechanism that involves degradation of cellular components, is essential for cell homeostasis. Although autophagy favours the lineage stability of regulatory T cells, the contribution of autophagy to the differentiation of effector CD4 T cells remains unclear. Here we show that autophagy selectively represses T helper 9 (TH9) cell differentiation. CD4 T cells lacking Atg3 or Atg5 have increased interleukin-9 (IL-9) expression upon differentiation into TH9 cells relative to Atg3- or Atg5-expressing control cells. In addition, the TH9 cell transcription factor, PU.1, undergoes K63 ubiquitination and degradation through p62-dependent selective autophagy. Finally, the blockade of autophagy enhances TH9 cell anticancer functions in vivo, and mice with T cell-specific deletion of Atg5 have reduced tumour outgrowth in an IL-9-dependent manner. Overall, our findings reveal an unexpected function of autophagy in the modulation of TH9 cell differentiation and antitumour activity, and prompt potential autophagy-dependent modulations of TH9 activity for cancer immunotherapy.Autophagy is a cellular process for recycling cell constituents, and is essential for T cell activation, but its function in T cell polarization is still unclear. Here the authors show that autophagy induces the degradation of transcription factor PU.1 to negatively modulate TH9 homeostasis and antitumour immunity.

Interleukin-9 Overexpression and Th9 Polarization Characterize the Inflamed Gut, the Synovial Tissue, and the Peripheral Blood of Patients With Psoriatic Arthritis

OBJECTIVE

To investigate the expression and tissue distribution of Th9-related cytokines in patients with psoriatic arthritis (PsA).

METHODS

Quantitative gene expression analysis of Th1, Th17, and Th9 cytokines was performed in intestinal biopsy samples obtained from patients with PsA, HLA-B27-positive patients with ankylosing spondylitis (AS), patients with Crohn's disease (CD), and healthy controls. Expression and tissue distribution of interleukin-23 (IL-23), IL-17, IL-22, IL-9, and IL-9 receptor (IL-9R) were evaluated by immunohistochemistry and confocal microscopy. Flow cytometry was used to study the frequency of Th9 cells among peripheral blood, lamina propria, and synovial fluid mononuclear cells. The functional relevance of IL-9R expression on epithelial cells was assessed in functional in vitro studies. Th9 cells in synovial tissue from patients with PsA were also studied.

RESULTS

Subclinical gut inflammation in PsA patients was characterized by a clear Th17 and Th22, but not Th1, polarized immune response. Unlike AS and CD, a strong and significant up-regulation of IL-9 was observed in PsA gut, especially among infiltrating mononuclear cells, high endothelial venules, and Paneth cells. IL-9-positive mononuclear cells were demonstrated to be in large part Th9 cells. IL-9 overexpression was accompanied by significant Paneth cell hyperplasia. Paneth cells strongly overexpressed IL-9R, and stimulation of epithelial cells, isolated from PsA patients, with IL-9 resulted in overexpression of α-defensin 5 and IL-23p19. Peripheral and synovial expansion of α4β7+ Th9 cells was also observed in patients with PsA. Increased expression of IL-9 and IL-9R was also found in synovial tissue.

CONCLUSION

Strong IL-9/Th9 polarization seems to be the predominant immunologic signature in patients in PsA.

Activation of Epithelial Signal Transducer and Activator of Transcription 1 by Interleukin 28 Controls Mucosal Healing in Mice With Colitis and Is Increased in Mucosa of Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

We investigated the roles of interleukin 28A (also called IL28A or interferon λ2) in intestinal epithelial cell (IEC) activation, studying its effects in mouse models of inflammatory bowel diseases (IBD) and intestinal mucosal healing.

METHODS

Colitis was induced in C57BL/6JCrl mice (controls), mice with IEC-specific disruption of Stat1 (Stat1IEC-KO), mice with disruption of the interferon λ receptor 1 gene (Il28ra-/-), and mice with disruption of the interferon regulatory factor 3 gene (Irf3-/-), with or without disruption of Irf7 (Irf7-/-). We used high-resolution mini-endoscopy and in vivo imaging methods to assess colitis progression. We used 3-dimensional small intestine and colon organoids, along with RNA-Seq and gene ontology methods, to characterize the effects of IL28 on primary IECs. We studied the effects of IL28 on the human intestinal cancer cell line Caco-2 in a wound-healing assay, and in mice colon wounds. Colonic biopsies and resected tissue from patients with IBD (n = 62) and patients without colon inflammation (controls, n = 23) were analyzed by quantitative polymerase chain rection to measure expression of IL28A, IL28RA, and other related cytokines; biopsy samples were also analyzed by immunofluorescence to identify sources of IL28 production. IECs were isolated from patient tissues and incubated with IL28; signal transducer and activator of transcription 1 (STAT1) phosphorylation was measured by immunoblots and confocal imaging.

RESULTS

Lamina propria cells in colon tissues of patients with IBD, and mice with colitis, had increased expression of IL28 compared with controls; levels of IL28R were increased in the colonic epithelium of patients with IBD and mice with colitis. Administration of IL28 induced phosphorylation of STAT1 in primary human and mouse IECs, increasing with dose. Il28ra-/-, Irf3-/-, Irf3-/-Irf7-/-, as well as Stat1IEC-KO mice, developed more severe colitis after administration of dextran sulfate sodium than control mice, with reduced epithelial restitution. Il28ra-/- and Stat1IEC-KO mice also developed more severe colitis in response to oxazolone than control mice. We found IL28 to induce phosphorylation (activation) of STAT1 in epithelial cells, leading to their proliferation in organoid culture. Administration of IL28 to mice with induced colonic wounds promoted mucosal healing.

CONCLUSIONS

IL28 controls proliferation of IECs in mice with colitis and accelerates mucosal healing by activating STAT1. IL28 might be developed as a therapeutic agent for patients with IBD.

Systemic interleukin-9 in inflammatory bowel disease: Association with mucosal healing in ulcerative colitis

AIM

To evaluate circulating IL9 in inflammatory bowel disease and disease-associated anemia/cachexia and assess its potential as a mucosal healing marker.

METHODS

Serum IL9 as well as other cytokines (IL1β, IL6, IL13, IFNγ, TNFα, and VEGF-A) were determined in 293 individuals: 97 patients with Crohn’s disease (CD) and 74 with ulcerative colitis (UC) and in 122 apparently healthy controls. The clinical activity of CD and UC was expressed in terms of the Crohn’s Disease Activity Index (CDAI) and the Mayo Scoring System (MDAI), respectively, and the severity of bowel inflammation in UC patients was assessed using Mayo endoscopic score. Cytokine concentrations were measured by a flow cytometry-based method using Luminex xMAP^® technology. High-sensitive C-reactive protein concentrations (hsCRP) were determined in CD and UC patients using the enhanced immunoturbidimetric method.

RESULTS

Systemic IL9 was significantly lower in healthy individuals [9 pg/mL (95%CI: 8.2-10)] than in patients with inflammatory bowel disease (IBD): both inactive [14.3 pg/mL (11.9-19.9)] and active [27.6 pg/mL (24.5-32), P < 0.0001]. Cytokine concentrations were significantly higher in active CD [27.4 pg/mL (23.4-32.2)] and in active UC [32.7 pg/mL (27-38.9)] compared to inactive diseases [15.9 pg/mL (10.8-23.4) in CD and 19.4 pg/mL (13.9-27.1) in UC, P = 0.001]. IL9 correlated weakly with CDAI (ρ = 0.32, P = 0.003) and MDAI (ρ = 0.35, P = 0.002) and strongly with endoscopic inflammation in UC (ρ = 0.74, P < 0.0001). As a negative marker of mucosal healing (MH), IL9 had an accuracy superior to hsCRP and IL6 [97% (P < 0.0001), 67% (P = 0.071), and 55% (P = 0.525), respectively]. IL9 was significantly higher in cachectic IBD patients [30.25 pg/mL (24.4-37.5) vs 21.88 pg/mL (18-26.5), P = 0.026] and negatively correlated with hemoglobin concentrations (ρ = -0.27, P < 0.001). Multiple regression showed IL1β and IL13 to be the independent predictors of circulating IL9 in healthy individuals, IFNγ or IL6 in active and inactive UC, respectively, and IL13 and VEGF-A in both active and inactive CD.

CONCLUSION

The systemic IL9 level is higher in IBD and corresponds with endoscopic inflammation, suggesting its possible application as a negative marker of mucosal healing in UC.

Intestinal dysbiosis and innate immune responses in axial spondyloarthritis

PURPOSE OF REVIEW

Inflammatory innate and adaptive immune cell responses to commensal bacteria underlie the pathogenesis of human chronic inflammatory diseases. Intestinal dysbiosis has been described in patients with spondyloarthritis (SpA) and seems to be correlated with histologic and immunologic alterations. Purpose of this review is to discuss the relationship occurring between intestinal dysbiosis and innate immune responses in patients with axial SpA.

RECENT FINDINGS

Intestinal dysbiosis and differential activation of intestinal immune responses in patients with SpA have been demonstrated. Furthermore, innate cells that appear to be involved in the pathogenesis of SpA may control intestinal homeostasis through induction of apoptotic cell death and deletion of activated commensal bacteria-specific T cells.

SUMMARY

Although the evidence shows that dysbiosis occurs in SpA, it is not clear the role of dysbiosis in regulating innate immune responses in SpA. Relationships between cause and effect remain to be answered.

VIDEO ABSTRACT

http://links.lww.com/COR/A34.

Interleukin-9 and T helper type 9 cells in rheumatic diseases

Interleukin (IL)-9 is a 28-30 kDa monomeric glycosylated polypeptide belonging to the IL-7/IL-9 family of proteins that bind to a composite receptor consisting of the private receptor IL-9R and the IL-2 receptor, gamma (IL-2RG), a common gamma subunit shared by the receptors of many different cytokines. The IL-9R is expressed widely and IL-9 impacts a number of effector cells, such as effector T cells, B cells, innate lymphoid cells, mast cells, polymorphonuclear cells, epithelial cells and smooth muscle cells, playing an important role in regulating inflammatory immunity. The critical role of IL-9 in promoting cellular and humoral immune responses makes it an important focus of potential therapeutic interventions. Recently, a defined subset of T helper type cells, Th9 cells, has been identified by the potent production of IL-9. The involvement of the Th9 cell subset has been described in many types of inflammatory diseases, namely atopic diseases, helminth infections, experimental autoimmune encephalomyelitis and ulcerative colitis. In this review, we summarize the IL-9 biological activities, highlighting roles for IL-9 and Th9 cells in rheumatoid and psoriatic arthritis, systemic vasculitis, systemic lupus erythematosus and systemic sclerosis.

Novel Insights into the Mechanisms of Gut Homing and Antiadhesion Therapies in Inflammatory Bowel Diseases

Therapeutic compounds interfering with T cell trafficking are a new column of inflammatory bowel disease (IBD) treatment. Currently, the anti-α4β7 integrin antibody vedolizumab is successfully used in the clinic and further drugs are likely to follow. Despite these clinical advances, the precise mechanistic background of their action is only gradually elucidated and still a matter of intensive research. Only recently, advances made with the help of new in vivo models and human studies have contributed to shape our concept of T cell trafficking in IBD by deciphering some important and so far unanswered questions. At the same time, basic and clinical data have generated new issues to be addressed on the way toward a clear perception of trafficking mechanisms and toward elucidation of the action of compounds interfering with this process. In this review, we will give a comprehensive outline of all components of T cell trafficking in regard to IBD before discussing the current knowledge concerning targeted interference with integrins in this complex network. Moreover, we will summarize remaining ambiguity and give an outlook on potential future targets.

The TNF family member TL1A induces IL-22 secretion in committed human Th17 cells via IL-9 induction

TL1A contributes to the pathogenesis of several chronic inflammatory diseases, including those of the bowel by enhancing TH1, TH17, and TH2 responses. TL1A mediates a strong costimulation of these TH subsets, particularly of mucosal CCR9+ T cells. However, the signaling pathways that TL1A induces in different TH subsets are incompletely understood. We investigated the function of TL1A on human TH17 cells. TL1A, together with TGF-β, IL-6, and IL-23, enhanced the secretion of IL-17 and IFN-γ from human CD4+ memory T cells. TL1A induced expression of the transcription factors BATF and T-bet that correlated with the secretion of IL-17 and IFN-γ. In contrast, TL1A alone induced high levels of IL-22 in memory CD4+ T cells and committed TH17 cells. However, TL1A did not enhance expression of IL-17A in TH17 cells. Expression of the transcription factor aryl hydrocarbon receptor, which regulates the expression of IL-22 was not affected by TL1A. Transcriptome analysis of TH17 cells revealed increased expression of IL-9 in response to TL1A. Blocking IL-9 receptor antibodies abrogated TL1A-induced IL-22 secretion. Furthermore, TL1A increased IL-9 production by peripheral TH17 cells isolated from patients with Crohn's disease. These data suggest that TL1A differentially induces expression of TH17 effector cytokines IL-17, -9, and -22 and provides a potential target for therapeutic intervention in TH17-driven chronic inflammatory diseases.

Increased IL-17A/IL-17F expression ratio represents the key mucosal T helper/regulatory cell-related gene signature paralleling disease activity in ulcerative colitis

BACKGROUND

T helper (T_h) and regulatory T (T_reg) cell-related cytokines are implicated in inflammatory bowel diseases, including ulcerative colitis (UC). While these cytokines are generally upregulated in inflamed mucosae, the key cytokine profile explaining disease severity has not been determined.

METHODS

The Rachmilewitz endoscopic index (REI) was assessed in 61 UC patients undergoing colonoscopy. Biopsies obtained from inflamed (REI 3-12) and noninflamed (REI 0-2) areas were analyzed by quantitative PCR for expression of mRNAs encoding cytokines and transcription factors related to Th1 (TNF-α, IFN-γ, IL-12p35, IL-12p40, and T-bet), Th2 (IL-4, IL-13, IL-33, and GATA3), Th17 (IL-17A, IL-17F, IL-21, IL-22, IL-23p19, IL-6, and RORC), Th9 (IL-9, IRF4, and PU.1), and Treg (TGF-β and Foxp3). Expression patterns associated with higher REI were determined by univariate and multivariate analyses.

RESULTS

Despite general upregulation, none of these mRNAs showed univariate correlation with REI in inflamed samples. Multiple regression analysis, however, found that joint expression of IL-17A, IL-17F, IL-21, RORC, and TGF-β was significantly predictive of REI (P < 0.0002, R² = 0.380), with major individual contributions by IL-17A (P < 0.0001) and IL-17F (P < 0.0001), which were associated with increased and decreased REI, respectively. Partial correlation analysis, validating this model, indicated differences between IL-17A and IL-17F in correlating with other targets. The IL-17A/IL-17F ratio showed a significant correlation with REI (r = 0.5124, P < 0.0001), whereas no other mRNAs were essentially predictive of REI.

CONCLUSIONS

Mucosal IL-17A/IL-17F ratio significantly correlates with endoscopic score in UC patients, accompanied by their disparate interactions with other T_h/T_reg-related genes.

Th9 Cells: New Member of T Helper Cell Family

T Helper cells (CD4+ T cells) constitute one of the key arms of adaptive immune responses. Differentiation of naïve CD4+ T cells into multiple subsets ensure a proper protection against multitude of pathogens in immunosufficient individual. After differentiation, T helper cells secrete specific cytokines that are critical to provide immunity against various pathogens. The recently discovered Th9 cells secrete the pleiotropic cytokine, IL-9. Although IL-9 was cloned more than 25 years ago and characterized as a Th2 cell-specific cytokine, not many studies were carried out to define the function of IL-9. This cytokine has been demonstrated to act on multiple cell types as a growth factor. After the discovery of Th9 cells as an abundant source of IL-9, renewed focus has been generated. In this chapter, I discuss the biology and development of IL-9-secreting Th9 cells. Furthermore, I highlight the role of Th9 cells and IL-9 in health and diseases.

An Overview of the Innate and Adaptive Immune System in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) are thought to develop as a result of complex interactions between host genetics, the immune system and the environment including the gut microbiome. Although an improved knowledge of the immunopathogenesis of IBDs has led to great advances in therapy such as the highly effective anti-tumor necrosis factor class of medications, a significant proportion of patients with Crohn's disease and ulcerative colitis do not respond to anti-tumor necrosis factor antibodies. Further understanding of the different immune pathways involved in the genesis of chronic intestinal inflammation is required to help find effective treatments for IBDs. In this review, the role of the mucosal innate and adaptive immune system in IBD is summarized, highlighting new areas of discovery which may hold the key to identifying novel predictive or prognostic biomarkers and new avenues of therapeutic discovery.

Rectal Delivery of a DNAzyme That Specifically Blocks the Transcription Factor GATA3 and Reduces Colitis in Mice

BACKGROUND & AIMS

GATA3 is a transcription factor that regulates T-cell production of cytokines. We investigated the role of GATA3 in development of colitis in mice.

METHODS

We performed quantitative polymerase chain reaction and immunofluorescence analyses of colon tissues from patients with Crohn's disease (n = 61) or ulcerative colitis (UC, n = 74) or from patients without inflammatory bowel diseases (n = 22), to measure levels of GATA3. Colitis was induced by administration of oxazolone or 2,4,6-trinitrobenzenesulfonic acid to control mice, mice with T-cell-specific deletion of GATA3, and mice with deletion of tumor necrosis factor receptor (TNFR) 1 and TNFR2 (TNFR double knockouts); some mice were given a GATA3-specific DNAzyme (hgd40) or a control DNAzyme via intrarectal administration, or systemic injections of an antibody to TNF before or during sensitization and challenge phase of colitis induction. Colon tissues were collected and immunofluorescence and histochemical analyses were performed. Lamina propria mononuclear cells and T cells were isolated and analyzed by flow cytometry or cytokine assays. Colonic distribution of labeled DNAzyme and inflammation were monitored by in vivo imaging (endoscopy) of mice.

RESULTS

Levels of GATA3 messenger RNA were higher in colon tissues from patients with UC, but not ileal Crohn's disease, than control tissues; levels of GATA3 correlated with levels of inflammatory cytokines (interleukin [IL] 9, IL17A, IL6, IL5, IL4, IL13, and TNF). We observed increased expression of GATA3 by lamina propria T cells from mice with colitis compared with controls. Mice with T-cell-specific deletion of GATA3 did not develop colitis and their colonic tissues did not produce inflammatory cytokines (IL6, IL9, or IL13). The DNAzyme hgd40 inhibited expression of GATA3 messenger RNA by unstimulated and stimulated T cells, and distributed throughout the inflamed colons of mice with colitis. Colon tissues from mice given hgd40 had reduced expression of GATA3 messenger RNA, compared with mice given a control DNAzyme. Mice given hgd40 did not develop colitis after administration of oxazolone or 2,4,6-trinitrobenzenesulfonic acid; lamina propria cells from these mice expressed lower levels of IL6, IL9, and IL13 than cells from mice given the control DNAzyme. Mini-endoscopic images revealed that hgd40 and anti-TNF reduced colon inflammation over 3 days; hgd40 reduced colitis in TNFR double-knockout mice.

CONCLUSIONS

Levels of GATA3 are increased in patients with UC and correlate with production of inflammatory cytokines in mice and humans. A DNAzyme that prevents expression of GATA3 reduces colitis in mice, independently of TNF, and reduces levels of cytokines in the colon. This DNAzyme might be developed for treatment of patients with UC.

Characterization of Th9 Cells in the Development of EAE and IBD

Encephalitogenic and colitogenic effector T cells have been implicated in the induction of experimental autoimmune encephalomyelitis (EAE) and inflammatory bowel disease (IBD), respectively. Effector functions of Th1 and Th17 cells have been well characterized and described for the induction and development of EAE and IBD; however, the recently identified Th9 cells have also been suggested to play an important role in these autoimmune pathologies. Th9 cells, primarily characterized by their high level of production of IL-9, are not only essential in controlling extracellular pathogens but also contribute to the development of autoimmunity and allergic inflammation. Furthermore, it was also demonstrated that IL-9 promotes Th17 cell-mediated tissue pathology in EAE and it compromises the barrier functions of the gut in IBD. In vivo adoptive transfer of in vitro differentiated Th9 cells induces the development of autoimmune tissue inflammation in EAE and IBD. Here we describe methods for in vitro differentiation of naïve murine CD4+ T cells to generate IL-9-producing Th9 cells and follow their effector functions in EAE and IBD murine models.

IL-9 Signaling Pathway: An Update

Since the discovery of IL-9 almost three decades back as a growth factor, we have come a long way to understand its pleiotropic functions in the immune system. Despite its many functions, IL-9 still remains as an understudied cytokine. In the last decade, renewed emphasis has been provided to understand the biology of IL-9. Any growth factor or cytokine signals via its cognate receptor to mediate biological functions. In this chapter, we discuss the IL-9 signal transduction in different cell types, which would then exert its distinct functions.

TH9 cells in skin disorders

Interleukin 9 secreting T_H9 cells have been proposed as the latest addition to the family of T helper cell subsets. While a growing body of evidence from animal models points to important roles for these cells in allergic inflammation of the lung, autoinflammation of the gastrointestinal tract, and tumor immunity, their role in skin immunity and skin immunopathology remains poorly defined. Interestingly, studies of T helper cells from healthy humans suggest that T_H9 cells are predominantly skin-homing and skin-resident and that they are involved in protection against extracellular pathogens. Thus, T_H9 cells have entered the stage as potential mediators of cutaneous pathology. However, under which conditions and by which mechanisms these cells contribute to skin immunity and disease still has to be investigated. Here, we review our current understanding of T_H9 cells as skin-tropic T helper cells and their involvement in skin pathology. Further, we discuss open questions with regard to the intricate nature of interleukin 9 producing T helper cells.

Th9 cells in inflammatory bowel diseases

Inflammatory bowel diseases are chronic, relapsing, immunologically mediated disorders of the gastrointestinal tract. Emerging evidence suggests a critical functional role of transcription factors and T cell-related cytokines in ulcerative colitis and Crohn's disease. Gut-residing T cells from patients with inflammatory bowel disease produce high amounts of IL-9. Experimental models of colitis highlighted that IL-9-producing T cells critically interfered with an intact barrier function of the intestinal epithelium by impacting cellular proliferation and tight junction molecules. The blockade of IL-9 was suited to significantly ameliorate the disease activity and severity in experimental models of inflammatory bowel disease thereby suggesting that targeting IL-9 might function as a novel targeted approach for therapy.

Distinct interferon-gamma and interleukin-9 expression in cutaneous and oral lichen planus

BACKGROUND

Cutaneous (CLP) and oral lichen planus (OLP) as the main subtypes of lichen planus (LP) present with different clinical manifestation and disease course, although their histopathologic features such as the band-like lymphocyte infiltrate and keratinocyte apoptosis are similar. So far, the underlying cellular and molecular mechanisms remain poorly understood.

OBJECTIVE

The aim of this study was to characterize and compare the in situ cellular infiltrates, cytokine expression profiles and apoptosis markers in CLP and OLP.

METHODS

Using immunofluorescence staining and laser scanning microscopy, we evaluated the cellular infiltrate (CD1a, CD3, CD4, CD8, CD21, CD57, CD123), cytokine expression (interleukin (IL)-1, IL-6, IL-9, IL-10, IL-17, IL-22, IL-23, tumour necrosis factor-α, transforming growth factor-β, interferon (IFN)-γ), and apoptosis markers (Fas, Fas ligand, cleaved caspase-3, TUNEL) of 21 anonymized biopsy specimens of LP (11 CLP, 10 OLP).

RESULTS

Among infiltrating cells mainly T cells and natural killer (NK) cells as well as plasmacytoid dendritic cells (DC) were observed. A predominance of CD8+ T cells was noted in OLP. In both CLP and OLP, T helper (Th)1, Th9, Th17, and Th22-type cytokines were expressed. The expression of IL-9, IFN-γ and IL-22 was higher in CLP compared to that of OLP (P = 0.0165; P = 0.0016; P = 0.052 respectively). Expression of Fas and Fas ligand as well as cleaved caspase-3-positive cells was observed in the epithelium of all LP samples.

CONCLUSIONS

The cell and cytokine patterns of CLP and OLP were partially distinct and generally resembled those reported for autoimmune diseases. The presence of CD8+ and NK cells as well as Fas/Fas ligand expression suggested that various pathways involved in keratinocyte apoptosis are relevant for LP. These results might help to establish targeted therapies for LP.

Human Vδ2 T cells are a major source of interleukin-9

Vδ2Vγ9 T cells are the dominant γδ T-cell subset in human peripheral blood. Vδ2 T cells recognize pyrophosphate molecules derived from microbes or tumor cells; hence, they play a role in antimicrobial and antitumor immunity. TGF-β, together with IL-15, induces a regulatory phenotype in Vδ2 T cells, characterized by forkhead box protein P3 (FoxP3) expression and suppressive activity on CD4 T-cell activation. We performed a genome-wide transcriptome analysis and found that the same conditions (TGF-β plus IL-15) strongly enhanced the expression of additional genes in Vδ2 T cells, including IKAROS family zinc finger 4 (IKZF4; Eos), integrin subunit alpha E (ITGAE; CD103/αEβ7), and IL9 This up-regulation was associated with potent IL-9 production as revealed by flow cytometry and multiplex analysis of cell culture supernatants. In contrast to CD4 and CD8 αβ T cells, γδ T cells did not require IL-4 for induction of intracellular IL-9 expression. Upon antigen restimulation of Vδ2 T cells expanded in vitro in the presence of TGF-β and IL-15, IL-9 was the most abundant among 16 analyzed cytokines and chemokines. IL-9 is a pleiotropic cytokine involved in various (patho)physiological conditions, including allergy and tumor defense, where it can promote antitumor immunity. Given the conspicuous sensitivity of many different tumors to Vδ2 T-cell-mediated killing, the conditions defined here for strong induction of IL-9 might be relevant for the development of Vδ2 T-cell-based immunotherapy.

Tofacitinib for the treatment of ulcerative colitis

INTRODUCTION

Management of patients with active ulcerative colitis (UC), one of the most frequent inflammatory bowel diseases in human beings, is mainly based on the use of mesalamine and corticosteroids. Since in the long-term, these two drugs may be ineffective in nearly one third of the patients, immunosuppressants and/or biologics are needed to control disease activity.

AREAS COVERED

The marked activation of JAK/STAT molecules in inflamed mucosa of UC patients and the demonstration that UC-associated mucosal injury is driven by soluble factors that signal through JAK/STAT pathways led to investigation of JAK inhibitors for the treatment of active UC. Tofacitinib, an oral inhibitor of the cytokine-driven JAK-STAT signalling cascade, has recently been proposed for the treatment of moderate-to-severe UC. Phase 2 study showed the efficacy of tofacitinib to induce clinical and endoscopic improvement/remission and the safety profile of the drug. Herein the authors review this compound.

EXPERT OPINION

The results obtained from clinical trials with tofacitinib suggest that this drug could be a new treatment option for patients with moderate to severe UC. However, further experimentation is needed to assess the efficacy of this drug in selected subgroups of patients as well as to maintain remission and to determine the long-term safety profile of the drug.

Cytokine Networks and T-Cell Subsets in Inflammatory Bowel Diseases

Pathogenesis of the inflammatory bowel diseases (IBDs), such as ulcerative colitis (UC) and Crohn's disease (CD), involve proinflammatory changes within the microbiota, chronic immune-mediated inflammatory responses, and epithelial dysfunction. Converging data from genome-wide association studies, mouse models of IBD, and clinical trials indicate that cytokines are key effectors of both normal homeostasis and chronic inflammation in the gut. Yet many questions remain concerning the role of specific cytokines in different IBDs within distinct regions of the gut, and regarding cellular mechanisms of action. In this article, we review current and emerging concepts concerning the role of cytokines in IBD with a focus on immune regulation, T cell subsets, and potential clinical applications.

Cytokine Networks and T-Cell Subsets in Inflammatory Bowel Diseases

Pathogenesis of the inflammatory bowel diseases (IBDs), such as ulcerative colitis (UC) and Crohn's disease (CD), involve proinflammatory changes within the microbiota, chronic immune-mediated inflammatory responses, and epithelial dysfunction. Converging data from genome-wide association studies, mouse models of IBD, and clinical trials indicate that cytokines are key effectors of both normal homeostasis and chronic inflammation in the gut. Yet many questions remain concerning the role of specific cytokines in different IBDs within distinct regions of the gut, and regarding cellular mechanisms of action. In this article, we review current and emerging concepts concerning the role of cytokines in IBD with a focus on immune regulation, T cell subsets, and potential clinical applications.

Cytokine-Induced Modulation of Colorectal Cancer

The emergence of novel immunomodulatory cancer therapies over the last decade, above all immune checkpoint blockade, has significantly advanced tumor treatment. For colorectal cancer (CRC), a novel scoring system based on the immune cell infiltration in tumors has greatly improved disease prognostic evaluation and guidance to more specific therapy. These findings underline the relevance of tumor immunology in the future handling and therapeutic approach of malignant disease. Inflammation can either promote or suppress CRC pathogenesis and inflammatory mediators, mainly cytokines, critically determine the pro- or anti-tumorigenic signals within the tumor environment. Here, we review the current knowledge on the cytokines known to be critically involved in CRC development and illustrate their mechanisms of action. We also highlight similarities and differences between CRC patients and murine models of CRC and point out cytokines with an ambivalent role for intestinal cancer. We also identify some of the future challenges in the field that should be addressed for the development of more effective immunomodulatory therapies.

The Role of T-Cell Subsets in Chronic Inflammation in Celiac Disease and Inflammatory Bowel Disease Patients: More Common Mechanisms or More Differences?

Background

Chronic intestinal inflammation due to noninfectious causes represents a growing health issue all over the world. Celiac disease as well as inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative and microscopic colitis involve uncontrolled T-cell activation and T-cell-mediated damage as common denominators. Therefore, diagnosis and treatment decisions clearly benefit from the knowledge of the intricacies of the systemic and the local T-cell activity.

Summary

Depending on the cytokine milieu, CD4⁺ T cells can differentiate into proinflammatory T helper 1 (Th1), anti-inflammatory Th2, antimicrobial Th17, pleiotropic Th9, tissue-instructing Th22 cells, and in the regulatory compartment forkhead box protein 3⁺ Treg, suppressive Tr1 or Th3 cells. Additionally, follicular Th cells provide B-cell help in antibody class switching; cytotoxic CD8⁺ T cells target virus-infected or tumor cells. This review discusses our current knowledge on the contribution of defined T-cell subpopulations to establishing and maintaining chronic intestinal inflammation in either of the above entities. It also puts emphasis on the differences in the prevalence of these diseases between Eastern and Western countries.

Key Messages

In celiac disease, the driving role of T cells in the lamina propria and in the epithelium mainly specific for two defined antigens is well established. Differences in genetics and lifestyle between Western and Eastern countries were instrumental in understanding underlying mechanisms. In IBD, the vast amount of potential antigens and the corresponding antigen-specific T cells makes it unlikely to find universal triggers. Increased mucosal CD4⁺ regulatory T cells in all four entities fail to control or abrogate local inflammatory processes. Thus, prevailing differences in the functional T-cell subtypes driving chronic intestinal inflammation in celiac disease and IBD at best allow some overlap in the treatment options for either disease.

Retinoic acid-primed human dendritic cells inhibit Th9 cells and induce Th1/Th17 cell differentiation

All-trans-retinoic acid plays a central role in mucosal immunity, where it promotes its synthesis by up-regulating CD103 expression on dendritic cells, induces gut tropic (α4β7(+) and CCR9(+)) T cells, and inhibits Th1/Th17 differentiation. Recently, murine studies have highlighted the proinflammatory role of retinoic acid in maintaining inflammation under a variety of pathologic conditions. However, as a result of limited human data, we investigated the effect of retinoic acid on human dendritic cells and CD4(+) T cell responses in the presence of polarizing (Th1/Th9/Th17) and inflammatory (LPS-induced dendritic cells) conditions. We report a novel role of retinoic acid in an inflammatory setup, where retinoic acid-primed dendritic cells (retinoic acid-monocyte-derived dendritic cells) up-regulated CCR9(+)T cells, which were observed to express high levels of IFN-γ in the presence of Th1/Th17 conditions. Retinoic acid-monocyte-derived dendritic cells, under Th17 conditions, also favored the induction of IL-17(+) T cells. Furthermore, in the presence of TGF-β1 and IL-4, retinoic acid-monocyte-derived dendritic cells inhibited IL-9 and induced IFN-γ expression on T cells. Experiments with naïve CD4(+) T cells, activated in the presence of Th1/Th17 conditions and absence of DCs, indicated that retinoic acid inhibited IFN-γ and IL-17 expression on T cells. These data revealed that in the face of inflammatory conditions, retinoic acid, in contrast from its anti-inflammatory role, could maintain or aggravate the intestinal inflammation.

A deleterious role for Th9/IL-9 in hepatic fibrogenesis

T helper 9 (Th9) cells, a recently recognized Th cell subset, are involved in autoimmune diseases. We aimed to investigate the role of Th9/interleukin-9 (IL-9) in the pathogenesis of hepatic fibrosis. Th9 and Th17 cells were quantified in chronic hepatitis B (CHB) patients with hepatic fibrosis, HBV-associated liver cirrhosis (LC) patients and healthy controls (HC). The percentages of Th9 and Th17 cells, concentrations of IL-9 and IL-17, as well as expression of IL-17, TNF-α, IL-6, IL-4, IL-21, TGF-β1 and IFN-γ were significantly increased in plasma of CHB and LC patients compared with those in HC. Splenic Th9 and Th17 cells, plasma concentrations and liver expression of IL-9 and IL-17A were significantly elevated in mice with hepatic fibrosis compared with controls. Neutralization of IL-9 in mice ameliorated hepatic fibrosis, attenuated the activation of hepatic stellate cells, reduced frequencies of Th9, Th17 and Th1 cells in spleen, and suppressed expression of IL-9, IL-17A, IFN-γ, TGF-β1, IL-6, IL-4 and TNF-α in plasma and liver respectively. Our data suggest a deleterious role of Th9/IL-9 in increasing hepatic fibrosis and exacerbating disease endpoints, indicating that Th9/IL9 based immunotherapy may be a promising approach for treating hepatic fibrosis.

Altered STAT4 Isoform Expression in Patients with Inflammatory Bowel Disease

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are the major forms of inflammatory bowel disease, and pathogenesis involves a complex interplay among genetic, environmental, and immunological factors. We evaluated isoform expression of the IL-12-activated transcription factor STAT4 in children with CD and UC.

METHODS

We collected biopsy samples from both patients newly diagnosed with CD and with UC. We further collected blood samples from patients newly diagnosed with CD and with UC as well as from patients who had a flare-up after being in clinical remission, and we examined the ratios of STAT4β/STAT4α mRNA. In addition to STAT4 isoforms, we measured the expression of the cytokines TNFα, IFNγ, granulocyte macrophage-colony stimulating factor, and IL-17 using polymerase chain reaction of biopsy samples and multiplex analysis of patient serum samples.

RESULTS

Ratios of STAT4β/STAT4α were increased in specific gastrointestinal tract segments in both patients with CD and those with UC that correlate with the location and severity of inflammation. In contrast, we did not observe changes in STAT4β/STAT4α ratios in biopsy specimens from patients with eosinophilic esophagitis. We also observed increased STAT4β/STAT4α ratios in the peripheral blood mononuclear cells of patients with UC and those with CD, compared with healthy controls. Ratios were normalized after patients were treated with steroids.

CONCLUSIONS

Collectively, these data indicate that STAT4 isoforms could be an important noninvasive biomarker in the diagnosis and treatment of inflammatory bowel disease and that expression of these isoforms might provide further insight into the pathogenesis of IBD.

IL-9 signaling affects central nervous system resident cells during inflammatory stimuli

Interleukin (IL) 9, a dominant cytokine in Th9 cells, has been proven to play a pathogenic role in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), by augmenting T cell activation and differentiation; however, whether IL-9 signaling affects central nervous system (CNS)-resident cells during CNS autoimmunity remains unknown. In the present study, we found that the IL-9 receptor (IL-9R) was highly expressed in astrocytes, oligodendrocyte progenitor cells (OPCs), oligodendrocytes and microglia cells, and that its expression was significantly upregulated in brain and spinal cord during EAE. In addition, IL-9 increased chemokine expression, including CXCL9, CCL20 and MMP3, in primary astrocytes. Although IL-9 had no effect on the proliferation of microglia cells, it decreased OPC proliferation and differentiation when in combination with other pro-inflammatory cytokines, but not with IFN-γ. IL-9 plus IFN-γ promoted OPC proliferation and differentiation. These findings indicate that CNS-restricted IL-9 signaling may be involved in the pathogenesis of MS/EAE, thus providing a potential therapeutic target for future MS/EAE treatment through disruption of CNS cell-specific IL-9 signaling.

The development and in vivo function of T helper 9 cells

The specialized cytokine secretion profiles of T helper (TH) cells are the basis for a focused and efficient immune response. On the twentieth anniversary of the first descriptions of the cytokine signals that promote the differentiation of interleukin-9 (IL-9)-secreting T cells, this Review focuses on the extracellular signals and the transcription factors that promote the development of what we now term TH9 cells, which are characterized by the production of this cytokine. We summarize our current understanding of the contribution of TH9 cells to both effective immunity and immunopathological disease, and we propose that TH9 cells could be targeted for the treatment of allergic and autoimmune disease.