Expression of IL-17 in human memory CD45RO+ T lymphocytes and its regulation by protein kinase A pathway

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Contribution of Interleukin-17A to Retinal Degenerative Diseases

Retinal degenerative diseases are a leading cause of vision loss and blindness throughout the world, characterized by chronic and progressive loss of neurons and/or myelin. One of the common features of retinal degenerative diseases and central neurodegenerative diseases is chronic neuroinflammation. Interleukin-17A (IL-17A) is the cytokine most closely related to disease in its family. Accumulating evidence suggests that IL-17A plays a key role in human retinal degenerative diseases, including age-related macular degeneration, diabetic retinopathy and glaucoma. This review aims to provide an overview of the role of IL-17A participating in the pathogenesis of retinal degenerative diseases, which may open new avenues for potential therapeutic interventions.

Exploring antibody repurposing for COVID-19: beyond presumed roles of therapeutic antibodies

The urgent need for a treatment of COVID-19 has left researchers with limited choice of either developing an effective vaccine or identifying approved/investigational drugs developed for other medical conditions for potential repurposing, thus bypassing long clinical trials. In this work, we compared the sequences of experimentally verified SARS-CoV-2 neutralizing antibodies and sequentially/structurally similar commercialized therapeutic monoclonal antibodies. We have identified three therapeutic antibodies, Tremelimumab, Ipilimumab and Afasevikumab. Interestingly, these antibodies target CTLA4 and IL17A, levels of which have been shown to be elevated during severe SARS-CoV-2 infection. The candidate antibodies were evaluated further for epitope restriction, interaction energy and interaction surface to gauge their repurposability to tackle SARS-CoV-2 infection. Our work provides candidate antibody scaffolds with dual activities of plausible viral neutralization and immunosuppression. Further, these candidate antibodies can also be explored in diagnostic test kits for SARS-CoV-2 infection. We opine that this in silico workflow to screen and analyze antibodies for repurposing would have widespread applications.

Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor α (TNF-α). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases.

IL-17D: A Less Studied Cytokine of IL-17 Family

The interleukin-17 (IL-17) family is a relatively new family of cytokines consisting of 6 related factors (IL-17A-IL-17F), while the receptor family consists of 5 members: IL-17RA-IL-17RE. IL-17A is the prototype member of this family, which is also the signature cytokine of T helper 17 (Th17) cells. Th17 cells are involved in the development of autoimmune disease, inflammation, and tumors. Although IL-17D is similar to IL-17A in its ability to induce inflammatory cytokine production, there are fewer studies on IL-17D. Recently, the role of IL-17D in tumors and infections has attracted our attention. Some knowledge of function of IL-17D has been gained by studies using nonmammalian species. In this review, we introduce the structural characteristics, expression patterns, and biological characteristics of IL-17D along with its potential function in the pathogenesis of disease.

Evidence for Associations Between Th1/Th17 "Hybrid" Phenotype and Altered Lipometabolism in Very Severe Graves Orbitopathy

PURPOSE

The purpose of this article is to investigate the characteristics of Th1-cell and Th17-cell lineages for very severe Graves orbitopathy (GO) development.

METHODS

Flow cytometry was performed with blood samples from GO and Graves disease (GD) patients and healthy controls, to explore effector T-cell phenotypes. Lipidomics was conducted with serum from very severe GO patients before and after glucocorticoid (GC) therapy. Immunohistochemistry and Western blotting were used to examine orbital-infiltrating Th17 cells or in vitro models of Th17 polarization.

RESULTS

In GD, Th1 cells predominated in peripheral effector T-cell subsets, whereas in GO, Th17-cell lineage predominated. In moderate-to-severe GO, Th17.1 cells expressed retinoic acid receptor-related orphan receptor-γt (RORγt) independently and produced interleukin-17A (IL-17A), whereas in very severe GO, Th17.1 cells co-expressed RORγt and Tbet and produced interferon-γ (IFN-γ). Increased IFN-γ-producing Th17.1 cells positively correlated with GO activity and were associated with the development of very severe GO. Additionally, GC therapy inhibited both Th1-cell and Th17-cell lineages and modulated a lipid panel consisting of 79 serum metabolites. However, in GC-resistant, very severe GO, IFN-γ-producing Th17.1 cells remained at a high level, correlating with increased serum triglycerides. Further, retro-orbital tissues from GC-resistant, very severe GO were shown to be infiltrated by CXCR3+ Th17 cells expressing Tbet and STAT4 and rich in triglycerides that promoted Th1 phenotype in Th17 cells in vitro.

CONCLUSIONS

Our findings address the importance of Th17.1 cells in GO pathogenesis, possibly promoting our understanding of the association between Th17-cell plasticity and disease severity of GO.

The IL-17 Family of Cytokines in Health and Disease

The interleukin 17 (IL-17) family of cytokines contains 6 structurally related cytokines, IL-17A through IL-17F. IL-17A, the prototypical member of this family, just passed the 25^th anniversary of its discovery. Although less is known about IL-17B-F, IL-17A (commonly known as IL-17) has received much attention for its pro-inflammatory role in autoimmune disease. Over the past decade, however, it has become clear that the functions of IL-17 are far more nuanced than simply turning on inflammation. Accumulating evidence indicates that IL-17 has important context- and tissue-dependent roles in maintaining health during response to injury, physiological stress, and infection. Here, we discuss the functions of the IL-17 family, with a focus on the balance between the pathogenic and protective roles of IL-17 in cancer and autoimmune disease, including results of therapeutic blockade and novel aspects of IL-17 signal transduction regulation.

IL-17 and limits of success

Interleukin-17 (IL-17) is a potent proinflammatory cytokine that protects a host against fungal and extracellular bacterial infections. On the other hand, excessive or dysregulated production of IL-17 underlines susceptibility to autoimmune disease. Consequently, blocking IL-17 has become an effective strategy for modulating several autoimmune diseases, including multiple sclerosis (MS), psoriasis, and rheumatoid arthritis (RA). Notably, however, IL-17 blockade remains ineffective or even pathogenic against important autoimmune diseases such as inflammatory bowel disease (IBD). Furthermore, the efficacy of IL-17 blockade against other autoimmune diseases, including type 1 diabetes (T1D) is currently unknown and waiting results of ongoing clinical trials. Coming years will determine whether the efficacy of IL-17 blockade is limited to certain autoimmune diseases or can be expanded to other autoimmune diseases. These efforts include new clinical trials aimed at testing second-generation agents with the goal of increasing the efficiency, spectrum, and ameliorating side effects of IL-17 blockade. Here we briefly review the roles of IL-17 in the pathogenesis of selected autoimmune diseases and provide updates on ongoing and recently completed trials of IL-17 based immunotherapies.

Novel key cytokines in allergy: IL-17, IL-22

The biology of the T cell cytokines Interleukin (IL-)17 and IL-22 has been a main focus in the field of clinical immunology in the last decade. This intensive interest in both cytokines has resulted in almost 5,000 scientific publications (www.pubmed.com) dealing with the molecular structure, extra- and intracellular signaling pathways, specific transcription factors and the function of IL-17 and IL-22. This review article highlights the main findings concerning IL-17 and IL-22 in the last years.

Avoiding contact allergens: from basic research to the in vitro identification of contact allergens

Allergic contact dermatitis (ACD) is a chemical-induced inflammatory skin disease. Contact allergens are low-molecular-weight chemicals that must react with proteins in order to become immunogenic. This interaction leads to the activation of innate immune and stress responses and to the formation of antigenic epitopes for T cells which are the effector cells of ACD. Due to the multitude of chemicals that surround us in our daily life and their potential sensitizing capacity, it is crucial to identify contact sensitizers before these chemicals are used in consumer products. Appropriate in vitro assays for hazard identification are urgently needed to replace animal-based assays. The EU-wide ban on sensitization testing of cosmetic ingredients in animals is in effect since March 2009 and the necessity to test more than 30,000 already marketed chemicals for their sensitizing potential under the EU regulation REACh has intensified the worldwide efforts to replace animal testing. We summarize here the current strategies to develop a battery of assays which allows the identification of contact allergens by in vitro alternatives to animal testing. Our main focus lies on the test systems recently developed within the EU project Sens-it-iv in which we participate.

Proinflammatory Cytokine Environments Can Drive Interleukin-17 Overexpression by γ/δ T Cells in Systemic Juvenile Idiopathic Arthritis

OBJECTIVE

Systemic-onset juvenile idiopathic arthritis (JIA) is speculated to follow a biphasic course, with an initial systemic disease phase driven by innate immune mechanisms and interleukin-1β (IL-1β) as a key cytokine and a second chronic arthritic phase that may be dominated by adaptive immunity and cytokines such as IL-17A. Although a recent mouse model points to a critical role of IL-17-expressing γ/δ T cells in disease pathology, in humans, both the prevalence of IL-17 and the role of IL-17-producing cells are still unclear.

METHODS

Serum samples from systemic JIA patients and healthy pediatric controls were analyzed for the levels of IL-17A and related cytokines. Whole blood samples were studied for cellular expression of IL-17 and interferon-γ (IFNγ). CD4+ and γ/δ T cells isolated from the patients and controls were assayed for cytokine secretion in different culture systems.

RESULTS

IL-17A was prevalent in sera from patients with active systemic JIA, while both ex vivo and in vitro experiments revealed that γ/δ T cells overexpressed this cytokine. This was not seen with CD4+ T cells, which expressed strikingly low levels of IFNγ. Therapeutic IL-1 blockade was associated with partial normalization of both cytokine expression phenotypes. Furthermore, culturing healthy donor γ/δ T cells in serum from systemic JIA patients or in medium spiked with IL-1β, IL-18, and S100A12 induced IL-17 overexpression at levels similar to those observed in the patients' cells.

CONCLUSION

A systemic JIA cytokine environment may prime γ/δ T cells in particular for IL-17A overexpression. Thus, our observations in systemic JIA patients strongly support a pathophysiologic role of these cells, as proposed by the recent murine model.

The relationship between circulating concentrations of interleukin 17 and C reactive protein in chronic spontaneous urticaria

Background

Up-regulation of interleukin 17 (IL-17) family cytokines and acute phase response have been observed in patients with chronic spontaneous urticaria (CSU). It has been demonstrated that IL-17 stimulates C-reactive protein (CRP) expression.

Aim

To determine relationship between circulating concentrations of IL-17 and CRP in CSU.

Methods

Concentrations of IL-17 in plasma and CRP in serum were measured in patients with CSU of varying severity and in the healthy subjects.

Results

IL-17 and CRP concentrations were significantly higher in CSU patients as compared to the healthy subjects. In addition, there were significant differences in IL-17 and CRP concentrations between CSU patients with mild, moderate-severe symptoms and the healthy subjects. CRP did not correlate significantly with IL-17.

Conclusions

Increased circulating IL-17 concentration may represent an independent index of systemic inflammatory response in CSU, which is not related to increased CRP concentration.

Cytokines IL-17 and IL-22 in the host response to infection

Cytokines IL-17 and IL-22 play pivotal roles in host defense against microbes and in the development of chronic inflammatory diseases. These cytokines are produced by cells that are often located in epithelial barriers, including subsets of T cells and innate lymphoid cells. In general, IL-17 and IL-22 can be characterized as important cytokines in the rapid response to infectious agents, both by recruiting neutrophils and by inducing the production of antimicrobial peptides. Although each cytokine induces an innate immune response in epithelial cells, their functional spectra are generally distinct: IL-17 mainly induces an inflammatory tissue response and is involved in the pathogenesis of several autoimmune diseases, whereas IL-22 is largely protective and regenerative. In this review, we compare IL-17 and IL-22, describing overlaps and differences in their cellular sources as well as their regulation, signaling, biological functions and roles during disease, with a focus on the contribution of these cytokines to the gut mucosal barrier during bacterial infection.

T cell immunity in the teleost digestive tract

Fish (along with cyclostomes) constitute the most ancient animal group in which an acquired immune system is present. As in higher vertebrates, both B and T lymphocytes cooperate in implementing an adequate response. Although there is still a debate on whether fish possess a true gut associated lymphoid tissue (GALT), the presence of diffuse B and T lymphocytes throughout all mucosal surfaces has been demonstrated in a wide variety of fish species. The lack of antibodies against T lymphocyte markers has hampered the performance of functional assays in both systemic and mucosal compartments. However, most components associated with T lymphocyte function have been identified in fish through extensive genomic research, suggesting similar functionalities for fish and mammalian T lymphocytes. Thus, the aim of this review is to briefly summarize what is known in teleost concerning the characteristics and functionalities of the different T cell subsets, to then focus on what is known to date regarding their presence and role in the gastrointestinal tract, through either direct functional assays or indirectly by conclusions drawn from transcriptomic analysis.

Expression Profile of Immune-Associated Genes in Nasal Polyps

Objectives:

We performed this study to investigate the expression profile of immune-associated genes and to probe the role of related genes in the immune pathogenesis of nasal polyps.

Methods:

Microarray analysis was used to find the expression profile of 491 immune-associated genes in nasal polyps. In validation studies, immunohistochemical staining and Western blot analysis were used to detect interleukin (IL)–17 and IL-17 receptor (IL-17R) in nasal polyps and controls.

Results:

Eighty-seven genes were differentially expressed in the immune-associated gene profile of nasal polyps, and 15 genes showed differential expression in both chips. In nasal polyp tissues, IL-17 was expressed mainly in the cytoplasm of plasma cells and to a lesser degree in the prickle cell layer of the epithelium and the acinus of the serous gland. In turbinates, IL-17 was also expressed in the same location, but the expression of IL-17 in nasal polyps and that in turbinates differed significantly (p > .05). Both IL-17 and IL-17R displayed specific bands in nasal polyps and turbinates, but the bands of IL-17 and IL-17R in nasal polyps were stronger than those in turbinates.

Conclusions:

The differentially expressed genes in immune-associated gene chips will provide clues about, and a theoretical foundation for, the pathogenesis of nasal polyps. Furthermore, IL-17 may play an important role in the occurrence of nasal polyps by overexpression.

The phosphodiesterase 4 inhibitor roflumilast augments the Th17-promoting capability of dendritic cells by enhancing IL-23 production, and impairs their T cell stimulatory activity due to elevated IL-10

Phosphodiesterase 4 (PDE4) inhibitors serve to prevent degradation of the intracellular second messenger cAMP, resulting in broad anti-inflammatory effects on different cell types including immune cells. Agents that elevate cAMP levels via activation of adenylate cyclase have been shown to imprint a Th17-promoting capacity in dendritic cells (DCs). Therefore, we studied the potential of therapeutically relevant PDE inhibitors to induce a pronounced Th17-skewing capacity in DCs. Here we show that mouse bone marrow-derived (BM-) DCs when treated with the PDE4 inhibitor roflumilast (ROF, trade name: Daxas) in the course of stimulation with LPS (ROF-DCs) evoked elevated IL-17 levels in cocultured allogeneic T cells. In addition, as compared with control settings, levels of IFN-γ remained unaltered, while contents of Th2 cytokines (IL-5, IL-10) were diminished. ROF enhanced expression of the Th17-promoting factor IL-23 in BM-DCs. In line, neutralizing antibodies specific for IL-23 or IL-6 when applied to DC/T cell cocultures partially inhibited the IL17-promoting effect of ROF-DCs. Furthermore, ROF-DCs displayed a markedly diminished allogeneic T cell stimulatory capacity due to enhanced production of IL-10, which was restored upon application of IL-10 specific neutralizing antibody to DC/T cell cocultures. Both the IL-17-inducing and impaired T cell stimulatory capacity of BM-DCs were mimicked by a specific activator of protein kinase A, while stimulation of EPACs (exchange proteins of activated cAMP) did not yield such effects. Taken together, our findings suggest that PDE4 inhibitors aside from their broad overall anti-inflammatory effects may enhance the Th17-polarizing capacity in DCs as an unwanted side effect.

Evaluation of Serum Interleukin-17 (IL-17) Levels as a Diagnostic Marker in Pancreatic Adenocarcinoma

BACKGROUND

Inflammatory cytokines modulate immune responses in the tumor microenvironment during progression. The role of interleukin (IL-17) in cancer is currently under debate. This study was conducted to investigate the serum levels of IL-17 in patients with pancreatic adenocarcinoma (PA) and the relationship with tumor progression and known prognostic parameters.

MATERIAL AND METHODS

Thirty-five patients with PA were investigated. Serum samples were obtained on first admission before treatment and follow-up. Both serum IL-17 levels were determined using enzyme-linked immunosorbent assay (ELISA). Age- and sex-matched 35 healthy controls were included in the analysis.

RESULTS

The median age at diagnosis was 61 years, range 38-84 years; 21 (60%) patients were men. The tumor was located in the head of pancreas in 24 (69%) patients. The most common metastatic site was liver in 20 patients with metastasis (n = 18, 90%). The median follow-up time was 24.0 weeks (range 1.0-191.0 weeks). At the end of the observation period, 12 (34%) patients experienced disease progression and 23 patients (66%) were dead. Forty-four percent of 18 metastatic patients who received palliative chemotherapy (CTx) were CTx-responsive. Median progression-free survival and overall survival of the whole group were 13.7 ± 2.3 weeks [95% confidence interval (CI) = 9-18 weeks] and 48.0 ± 12.8 weeks (95% CI = 23-73 weeks), respectively. The baseline serum IL-17 levels were significantly higher in patients with PA than in the control group (p = 0.001). Moreover, serum IL-17 levels were significantly higher in the patients with large pathologic tumor status and low albumin levels (p = 0.04 and p = 0.03, respectively). However, serum IL-17 assays had no prognostic roles on outcome.

CONCLUSION

Although serum levels of IL-17 assays were found to be diagnostic value, no predictive and prognostic value was determined in PA patients.

IL-17-producing γδT cells are regulated by estrogen during development of experimental arthritis

Interleukin-17 (IL-17) drives inflammation and destruction of joints in rheumatoid arthritis (RA). The female sex hormone 17β-estradiol (E2) inhibits experimental arthritis. γδT cells are significant producers of IL-17, thus the aim of this study was to investigate if E2 influenced IL-17(+) γδT cells during arthritis development using a variety of experimental RA models: collagen-induced arthritis (CIA); antigen-induced arthritis (AIA); and collagen antibody-induced arthritis (CAIA). We demonstrate that E2 treatment decreases IL-17(+) γδT cell number in joints, but increases IL-17(+) γδT cells in draining lymph nodes, suggesting an E2-mediated prevention of IL-17(+) γδT cell migration from lymph nodes to joints, in concert with our recently reported effects of E2 on Th17 cells (Andersson et al., 2015). E2 did neither influence the general γδT cell population nor IFNγ(+) γδT cells, implying a selective regulation of IL-17-producing cells. In conclusion, this study contributes to the understanding of estrogen's role in autoimmune disease.

Update on the role of Interleukin 17 in rheumatologic autoimmune diseases

Interleukin 17 is a proinflammatory cytokine produced by CD4+ T cells when in the presence of a distinct set of cytokines and other cells. Preclinical and clinical studies have assigned a role to IL-17 in tissue inflammation and damage in patients with rheumatoid arthritis, psoriasis and psoriatic arthritis, ankylosing spondylitis and systemic lupus erythematosus. Antibodies blocking the action of IL-17 have already been approved to treat patients with psoriasis and it is expected that they may also benefit patients with other rheumatic diseases.

Th22 cells in allergic disease

During the last decade, the field of T cell immunology started to confuse the scientific community. More and more subtypes of T helper cells and their counterparts in the innate immune system are described. We are just at the beginning to understand which specific function the distinct subtypes fulfill. Th22 cells are terminally differentiated and very specialized T helper cells characterized by the secretion of their signature cytokine IL-22 and lack of IL-4, IL-17 and IFN-γ. The main function of Th22 cells is to protect epithelial barrier organs such as skin and lung, but also to modulate inflamed and injured tissue. This review summarizes our current knowledge on Th22 cells and their function in allergic disease.

Cite this as Eyerich K, Eyerich S. Th22 cells in allergic disease. Allergo J Int 2015;24:1–7 DOI: 10.1007/s40629-015-0039-3

Immunopathogenesis of ocular Behçet's disease

Behçet's disease (BD) is a chronic recurrent systemic inflammatory disorder of unknown etiology characterized by oral and genital ulcerations, skin lesions, and uveitis. The ocular involvement of BD, or Behçet's uveitis (BU), is characterized by panuveitis or posterior uveitis with occlusive retinal vasculitis and tends to be more recurrent and sight threatening than other endogenous autoimmune uveitides, despite aggressive immunosuppression. Although pathogenesis of BD is unclear, researches have revealed that immunological aberrations may be the cornerstone of BD development. General hypothesis of BD pathogenesis is that inflammatory response is initiated by infectious agents or autoantigens in patients with predisposing genetic factors and perpetuated by both innate and acquired immunity. In addition, a network of immune mediators plays a substantial role in the inflammatory cascade. Recently, we found that the immunopathogenesis of BU is distinct from other autoimmune uveitides regarding intraocular effector cell profiles, maturation markers of dendritic cells, and the cytokine/chemokine environment. In addition, accumulating evidence indicates the involvement of Th17 cells in BD and BU. Recent studies on genetics and biologics therapies in refractory BU also support the immunological association with the pathogenesis of BU. In this review, we provide an overview of novel findings regarding the immunopathogenesis of BU.

IL-17 in the rheumatologist's line of sight

Over the past decades, the identification of several new cytokines, including interleukin (IL)-17 and IL-23, and of new T helper cell subsets, including Th17 cells, has changed the vision of immunological processes. The IL-17/Th17 pathway plays a critical role during the development of inflammation and autoimmunity, and targeting this pathway has become an attractive strategy for a number of diseases. This review aims to describe the effects of IL-17 in the joint and its roles in the development of autoimmune and inflammatory arthritis. Furthermore, biotherapies targeting directly or indirectly IL-17 in inflammatory rheumatisms will be developed.

Increased levels of circulating Th17 cells in quiescent versus active Crohn's disease

BACKGROUND AND AIMS

Th17 cells, a subset of CD4+ T cells that produce interleukin (IL)-17A, IL-17F, IL-21, IL-22, IL-26, and the chemokine CCL20 are critically involved in the mucosal inflammation observed in Crohn's disease (CD). However, their role as mediators of inflammation in CD has been questioned by a recent clinical trial in which anti-IL-17A (secukinumab) treatment was ineffective. Besides being pro-inflammatory, Th17-related cytokines mediate mucosal protective functions. We aimed to investigate the role of Th17 cells in CD inflammation.

METHODS

Blood samples from 26 patients with active CD and 10 healthy controls (HC) were analyzed for levels of IL-17A-, IL-21- and IL-22-producing CD45RO+CD4+ T cells using multicolor flow cytometry. Samples were analyzed before and during adalimumab treatment to compare intra-individual changes during active and quiescent disease.

RESULTS

CD patients had statistically significantly higher levels of IL-17-A-, IL-21- and IL-22-producing CD45RO+CD4+ T cells in both active and quiescent disease compared with HC. Baseline levels of IL-21 and IL-22 producing CD45RO+CD4+ T cells correlated inversely with mucosal inflammation estimated by fecal calprotectin. Patients who responded to adalimumab treatment demonstrated a 2- to 3-fold increase in levels of IL-17A- and IL-21-producing CD45RO+CD4+ T cells in quiescent disease compared with active disease.

CONCLUSION

Our data support the involvement of Th17 cells and IL-21- and IL-22-producing CD45RO+CD4+ T cells in CD. Because patients had higher levels in quiescent disease compared with active CD, we question whether Th17 cells are promoters of inflammation. Instead, Th17 cells may counterbalance inflammation and maintain gut homeostasis.

Expression of Th17-related genes in PHA/IL-2-activated human T cells by Fas signaling via caspase-1- and Stat3-dependent pathway

T helper 17 (Th17) cells, which produce interleukin 17 (IL-17), are involved in the pathogenesis of autoimmune diseases and inflammatory conditions. Th17 cells have been detected in many Fas ligand-positive tumors. This study investigates the expression of Th17-related genes in PHA/IL-2-activated human T cells upon Fas ligation. Activated T cells transiently express RORγt, IL-17A, and IL-17F. A subsequent Fas receptor stimulation or contact with FasL-expressing glioma cells significantly prolongs the induction of RORγt and Th17-related cytokines. Treatments with inhibitors of caspase-1 and Stat3 reduce the Fas-signal-associated induction of RORγt, IL-17A, and IL-17F, as well as the phosphorylation of Stat3. Although the ligation of Fas results in caspase-8 cleavage and ERK1/2 phosphorylation, inhibitors for caspase-8 and MEK have no effect on the expressions of RORγt, IL-17A, and IL-17F. The results suggest that the Fas signal favors the Th17-phenotypic features of human T cells through the caspase-1/Stat3 signaling pathway.

Halofuginone prevents estrogen-deficient osteoporosis in mice

Osteoporosis is characterized by enhanced activity of osteoclasts relative to that of osteoblasts. Thus, the principal means of treating the most common form of osteoporosis, namely that attending menopause, is inhibition of osteoclast formation or function. We have demonstrated that the inflammatory cytokine, IL-17, mediates estrogen-deficient osteoporosis, in mice, and that genetic blockade of its function prevents ovariectomy-induced bone loss. We herein report that the febrifugine derivative, halofuginone, a small molecule drug, reduces abundance of Th-17 cells in mice and prevents estrogen-deficient osteoporosis by diminishing bone resorption without impacting osteogenesis. In keeping with IL-17 mediating its osteoclastogenic effects by promoting RANK ligand expression by osteoblasts, halofuginone does not directly inhibit the bone resorptive cell. Thus, halofuginone, which is presently FDA-approved for treatment of scleroderma, is a candidate therapeutic for post-menopausal osteoporosis.

Immunovirological parameters and cytokines in HIV infection

Although modern combined antiretroviral therapies (cART) result in lower morbidity and mortality and a visible improvement of clinical and laboratory parameters in HIV-infected, it is known that their long-term use contributes to appearance of the many events unrelated to AIDS such as cardiovascular diseases, cancer and osteoporosis, comorbidities which have been proposed as some of the most important that deprive the majority of infected to present an even better prognosis. This is because even with a decrease in inflammation and immune activation after drug intervention to the patient, these parameters remain higher than those shown by healthy individuals and the imbalance of cytokine profiles also persists. Therefore, evaluations of other biomarkers in clinical practice are needed to complement the exams already carried out routinely and allow more effective monitoring of HIV patients. This review aims to investigate the role of cytokines as potential markers showing studies on their behavior in various stages of HIV infection, with or without cART.

Clinical significance of the ratio between FOXP3 positive regulatory T cell and interleukin-17 secreting cell in renal allograft biopsies with acute T-cell-mediated rejection

The aim of this study is to investigate the clinical significance of the ratio between interleukin-17 (IL-17) secreting cell and FOXP3-positive regulatory T cell (FOXP3(+) Treg) infiltration in renal allograft tissues with acute T-cell-mediated rejection (ATCMR). Fifty-six patients with biopsy-proven ATCMR were included. Infiltration of FOXP3(+) Treg and IL-17-secreting cells was evaluated with immunostaining for FOXP3 or IL-17 on the biopsy specimens, and the patients were divided into the FOXP3 high group (Log FOXP3/IL-17 > 0·45) or the IL-17 high group (Log FOXP3/IL-17 < 0·45). We compared the allograft function, severity of tissue injury, and clinical outcome between the two groups. In the IL-17 high group, allograft function was significantly decreased compared with the FOXP3 high group (P < 0·05). The severity of interstitial and tubular injury in the IL-17 high group was higher than the FOXP3 high group (P < 0·05). The proportions of steroid-resistant rejection, incomplete recovery and recurrent ATCMR were higher in the IL-17 high group than in the FOXP3 high group (all indicators, P < 0·05). The IL-17 high group showed lower 1-year (54% versus 90%, P < 0·05) and 5-year (38% versus 85%, P < 0·05) allograft survival rates compared with the FOXP3 high group. Multivariate analysis revealed that the FOXP3/IL-17 ratio was a significant predictor for allograft outcome. The FOXP3/IL-17 ratio is a useful indicator for representing the severity of tissue injury, allograft dysfunction and for predicting the clinical outcome of ATCMR.

Enrichment of circulating interleukin-17-secreting interleukin-23 receptor-positive γ/δ T cells in patients with active ankylosing spondylitis

OBJECTIVE

Ankylosing spondylitis (AS) is a common inflammatory arthritis affecting primarily the axial skeleton. IL23R is genetically associated with AS. This study was undertaken to investigate and characterize the role of interleukin-23 (IL-23) signaling in AS pathogenesis.

METHODS

The study population consisted of patients with active AS (n = 17), patients with psoriatic arthritis (n = 8), patients with rheumatoid arthritis, (n = 9), and healthy subjects (n = 20). IL-23 receptor (IL-23R) expression in T cells was determined in each subject group, and expression levels were compared.

RESULTS

The proportion of IL-23R-expressing T cells in the periphery was 2-fold higher in AS patients than in healthy controls, specifically driven by a 3-fold increase in IL-23R-positive γ/δ T cells in AS patients. The proportions of CD4+ and CD8+ cells that were positive for IL-17 were unchanged. This increased IL-23R expression on γ/δ T cells was also associated with enhanced IL-17 secretion, with no observable IL-17 production from IL-23R-negative γ/δ T cells in AS patients. Furthermore, γ/δ T cells from AS patients were heavily skewed toward IL-17 production in response to stimulation with IL-23 and/or anti-CD3/CD28.

CONCLUSION

Recently, mouse models have shown IL-17-secreting γ/δ T cells to be pathogenic in infection and autoimmunity. Our data provide the first description of a potentially pathogenic role of these cells in a human autoimmune disease. Since IL-23 is a maturation and growth factor for IL-17-producing cells, increased IL-23R expression may regulate the function of this putative pathogenic γ/δ T cell population.

Increased IL-17A expression in granulomas and in circulating memory T cells in sarcoidosis

OBJECTIVE

Sarcoidosis is a systemic inflammatory disorder characterized by granulomas. Although the aetiology is unknown, sarcoidosis is thought to be mediated by Th1 lymphocytes. Recently, IL-17A has been implicated in granuloma formation in various diseases, including tuberculosis. Therefore, we hypothesized that Th17 cells play a role in sarcoidosis, paralleling recent findings in autoimmune diseases such as RA. The aim of our study was to investigate the role of Th17 cells in sarcoidosis.

METHODS

T cells were investigated by intracellular flow cytometry and immunohistochemistry, in blood, bronchoalveolar lavages (BALs) and bronchial mucosal biopsies from a cohort of newly diagnosed sarcoidosis patients and healthy controls.

RESULTS

Circulating memory CD4(+) T-cell populations of sarcoidosis patients contained significantly increased proportions of IL-17A(+) cells when compared with healthy controls. Interestingly, proportions of IL-17A/IFN-γ and IL-17A/IL-4 double-producing cells were significantly increased in blood of sarcoidosis patients and were present in substantial numbers in BAL. In granuloma-containing, but not in non-granulomatous sarcoidosis biopsies, we found significantly increased numbers of IL-17A(+) T cells, located in and around granulomas throughout the lamina propria. IL-22(+) T cells were increased in the subepithelial layer.

CONCLUSIONS

Enhanced IL-17A expression in granulomas and the presence of IL-17A(+), IL-17A(+)IFN-γ(+) and IL-17A(+)IL-4(+)memory Th cells in the circulation and BAL indicate Th17 cell involvement in granuloma induction or maintenance in sarcoidosis. Therefore, neutralization of IL-17A activity may be a novel strategy to treat sarcoidosis.

Functional relevance of T helper 17 (Th17) cells and the IL-17 cytokine family in inflammatory bowel disease

The recent discovery and characterization of T helper 17 cells (Th17) and their signature cytokines (IL-17) represents a hallmark in T-cell immunobiology by providing a new distinctive pathway for the communication between adaptive and innate immunity. From the six members of the IL-17 cytokine family presently known, at least two have evident proinflammatory qualities and are involved in several chronic inflammatory disorders, including inflammatory bowel disease (IBD). IL-17A and IL-17F are abundantly found in inflamed IBD mucosa, suggesting their pivotal role in IBD. However, the precise implication of IL-17 cytokine family members in IBD pathogenesis and the mechanisms regulating their secretion are incompletely understood. Importantly, recent findings suggest that beyond IL-17 production-Th17 cells may secret a plethora of other effector cytokines such as IL-21, IL-22, and IL-9- which is in part induced by its own IL-9 production. However, the use of anti-IL-17 therapeutic strategies in experimental models of chronic inflammation results in disease-ameliorating effects suggesting their potential use in IBD patients. In this review article we discuss the latest findings on the role of Th17 cells and IL-17 family members in IBD immunopathology, as well as research perspectives.

Peripheral T(h)1/T(h)2/T(h)17/regulatory T-cell balance in asthmatic pregnancy

Asthma is a common chronic disease that may complicate pregnancy and a risk factor for complications; however, immunological mechanisms of the bilateral interactions between asthma and pregnancy are not fully understood. Healthy gestation is characterized by a sensitive balance of T(h)1/T(h)2/T(h)17/regulatory T (Treg) cells that may be altered in asthmatic pregnancy. The aim of this study was to describe the prevalence of these cell subsets in asthmatic compared with healthy pregnancy. The prevalence of T(h)1, T(h)2, T(h)17 and Treg lymphocytes was identified by cell surface and intracellular marker staining in blood samples of 24 healthy non-pregnant (HNP), 23 healthy pregnant (HP), 15 asthmatic non-pregnant (ANP) and 15 asthmatic pregnant (AP) women using flow cytometry. The T(h)1/T(h)2 cell ratio was decreased in both HP and ANP compared with HNP women; however, no further decrease was observed in the AP group. The T(h)17/Treg ratio was decreased in HP, but not in AP women, compared with HNP data. Healthy pregnancy increased Treg cell prevalence compared with HNP data (4.64% versus 2.98%; P < 0.05), and this pregnancy-induced elevation was absent in AP women (2.52% versus 4.64%; P < 0.05). T(h)17 cell prevalence was similar in the HP and HNP groups (2.78% versus 3.17%; P > 0.05). Asthma increased T(h)17 prevalence in non-pregnant patients (3.81% versus 3.17%; P < 0.05), and this asthma-specific increase of T(h)17 cell prevalence was also observed in AP patients (AP versus HP: 3.44% versus 2.78%; P < 0.05). The abnormal asthma-dependent T(h)17 elevation together with blunted Treg increase may play a role in the compromised immune tolerance characterizing asthmatic pregnancy.

Marked induction of c-Maf protein during Th17 cell differentiation and its implication in memory Th cell development

Until recently, effector T helper (Th) cells have been classified into two subsets, Th1 and Th2 cells. Since the discovery of Th17 cells, which produce IL-17, much attention has been given to Th17 cells, mainly because they have been implicated in the pathogenesis of various inflammatory diseases. We have performed transcriptome analysis combined with factor analysis and revealed that the expression level of c-Maf, which is considered to be important for Th2 differentiation, increases significantly during the course of Th17 differentiation. The IL-23 receptor (IL-23R), which is important for Th17 cells, is among putative transcriptional targets of c-Maf. Interestingly, the analysis of c-Maf transgenic Th cells revealed that the overexpression of c-Maf did not lead to the acceleration of the early stage of Th17 differentiation but rather to the expansion of memory phenotype cells, particularly with Th1 and Th17 traits. Consistently, mouse wild-type memory Th cells expressed higher mRNA levels of c-Maf, IL-23R, IL-17, and IFN-γ than control cells; in contrast, Maf(-/-) memory Th cells expressed lower mRNA levels of those molecules. Thus, we propose that c-Maf is important for the development of memory Th cells, particularly memory Th17 cells and Th1 cells.

Increased prevalence of IL-17-producing peripheral blood lymphocytes in pre-eclampsia

PROBLEM

Systemic inflammation is a dominant component in the pathogenesis of pre-eclampsia. Besides the imbalance of Th1 and Th2 cells, alterations of the prevalence of Th17 and regulatory T cells have also been suggested to contribute to inflammation. We aimed to describe the prevalence of these four CD4 lymphocyte subtypes in pre-eclampsia and normal pregnancy, along with that of IL-17-producing CD8 and NK cells.

METHOD OF STUDY

Twenty pre-eclamptic and 22 normal pregnant women were enrolled in this study. Using flow cytometry, we determined the prevalence of IL-17-producing cells among the CD4, CD8 and NK cell subsets. Furthermore, we measured the prevalence of CD4+ Tregs, and Th1/Th2 cells were characterized using cell surface chemokine receptor markers.

RESULTS

We demonstrated that there is a shift not only in the Th1/Th2 but also in the Th17/Treg balance favouring skewness towards a pro-inflammatory status in pre-eclampsia. The proportion of CD8 and NK cells that express IL-17 was also higher in pre-eclampsia.

CONCLUSION

The prevalence of IL-17-producing CD4, CD8 and NK cells is elevated in pre-eclampsia, indicating that both the innate and adaptive arms of the immune system are involved in the development of the exaggerated maternal systemic inflammation observed in this pregnancy-specific disorder.

Review: T helper 17 cells: their role in glomerulonephritis

T helper (Th) cells are an integral part of the host's immune response to eliminate invading pathogens. However, autoimmune or 'autoinflammatory' diseases can develop if Th cell responses are not effectively regulated. Several subsets of Th cells exist, including the Th17 subset that produces interleukin-17A, important in experimental models of organ-specific autoimmune inflammation. Its discovery has explained paradoxical observations in model systems thought to be Th1 mediated but were exacerbated in the absence of interferon-gamma, the prototypic Th1 effector cytokine. Th17 cells express unique transcription factors and secrete a unique pattern of cytokines. Interleukin-17A induces pro-inflammatory cytokines and chemokines and mediates neutrophil recruitment. Th17 cells have a reciprocal relationship with T regulatory cells and can also mediate suppression of Th1 responses. Recent studies also suggest that Th17 cells are not terminally differentiated but can switch into Th1 cells. Th17 cells have themselves been recently shown to induce antigen-specific cell-mediated proliferative glomerulonephritis. There is increasing evidence implicating Th17 cells in anti-glomerular basement membrane disease, lupus nephritis and pauci-immune glomerulonephritis. This review will review the discovery of the Th17 subset, its properties, its relationship with other Th subsets and assess the current evidence implicating Th17 cells in glomerulonephritis.

Potentiation of Th17 cytokines in aging process contributes to the development of colitis

Th17 cells, which produce IL-17 and IL-22, promote autoimmunity in mice and have been implicated in the pathogenesis of autoimmune/inflammatory diseases in humans. However, the Th17 immune response in the aging process is still not clear. In the present study, we found that the induction of IL-17-producing CD4(+) T cells was significantly increased in aged individuals compared with young healthy ones. The mRNA expression of IL-17, IL-17F, IL-22, and RORC2 was also significantly increased in aged people. Similar to humans, Th17 cells as well as mRNAs encoding IL-17, IL-22 and RORγt were dramatically elevated in naïve T cells from aged mouse compared to young ones. In addition, CD44 positive IL-17-producing CD4(+) T cells were significantly higher in aged mice, suggesting that memory T cells are an important source of IL-17 production. Furthermore, the percentage of IL-17-producing CD4(+) T cells generated in co-culture with dendritic cells from either aged or young mice did not show significant differences, suggesting that dendritic cells do not play a primary role in the elevation of Th17 cytokines in aged mouse cells. Importantly, transfer of CD4(+)CD45Rb(hi) cells from aged mice induced more severe colitis in RAG(-/-) mice compared to cells from young mice, Taken together, these results suggest that Th17 immune responses are elevated in aging humans and mice and may contribute to the increased development of inflammatory disorders in the elderly.

IL-17 and IL-22: siblings, not twins

T helper (Th) cell subsets secrete cytokines that regulate other immune cells. Interleukin (IL)-17 and IL-22 belong to a new class of cytokines with predominant effects on epithelial cells. Thus, these cytokines are key molecules in several disease processes. IL-17 and IL-22 are released by leukocytes such as Th and natural killer cell populations. Both IL-17 and IL-22 induce an innate immune response in epithelial cells, but their functional spectra are generally distinct. IL-17 induces an inflammatory tissue response and is involved in the pathogenesis of several autoimmune diseases, whereas IL-22 is protective/regenerative. This review juxtaposes IL-17 and IL-22 and describes overlaps and differences regarding their cellular sources, biochemical structure, signaling cascades in target cells, and function.

Induced Sézary syndrome PBMCs poorly express immune response genes up-regulated in stimulated memory T cells

BACKGROUND

Dysfunctions in memory T cells contribute to various inflammatory autoimmune diseases and neoplasms. We hypothesize that investigating the differences of genetic profiles between resting and activated naïve and memory T cells may provide insight into the characterization of abnormal memory T cells in diseases, such as Sézary syndrome (SS), a neoplasm composed of CD4(+) CD45RO(+) cells.

OBJECTIVE

We determined genes distinctively expressed between resting and activated naive and memory cells. Levels of up-regulated genes in resting and activated memory cells were measured in SS PBMCs, which were largely comprised of CD4(+) CD45RO(+) cells, to quantitatively assess how different Sézary cells were from memory cells.

METHODS

We compared gene expression profiles using high-density oligo-microarrays between resting and activated naïve and memory CD4(+) T cells. Differentially expressed genes were confirmed by qRT-PCR and immunoblotting. Levels of genes up-regulated in activated and resting memory T cells were determined in SS PBMCs by qRT-PCR.

RESULTS

Activated memory cells expressed greater numbers of immune-mediated genes involved in effector function compared to naïve cells in our microarray analysis and qRT-PCR. Nine out of 14 genes with enhanced levels in activated memory cells had reduced levels in SS PBMCs (p<0.05).

CONCLUSIONS

Activation of memory and naïve CD4(+) T cells revealed a diverging gap in gene expression between these subsets, with memory cells expressing immune-related genes important for effector function. Many of these genes were markedly depressed in SS patients, implying Sézary cells are markedly impaired in mounting immune responses compared to memory cells.

Th-17 cells in the lungs?

Naive CD4 cells are capable of integrating signals from antigen-activated cells of the innate immune system and differentiating into effector CD4 cells, also termed T helper (Th) cells. According to the traditional paradigm explaining adaptive CD4 cell responses, there are two subsets of Th cells: the Th-1 and Th-2 subset. Each of these subsets undergoes a distinct differentiation pathway (a pathway that is characterized by a unique profile of cytokine production and has specific immunoregulatory functions). However, recent studies in mouse models have forwarded evidence of a third subset of Th cells: the Th-17 subset. As indicated predominantly in studies on mice, the Th-17 subset is characterized by an ability to produce the neutrophil-mobilizing cytokine IL-17 in response to stimulation with the cytokine IL-23, an IL-12-related cytokine released from antigen-presenting cells. There is now a growing body of evidence from animal models that the Th-17 subset plays an important role in host defence in the lungs and other organs. Altered IL-17 levels have also been demonstrated in human patients with asthma, exacerbations of cystic fibrosis or following lung transplantation. There is now also evidence that the Th-17 subset is functionally distinct from the Th-2 subset but little is known of the functional inter-relationship between the Th-1 and Th-17 cell subsets; this is particularly true in human lungs. It has been proposed that the Th-17 subset plays a unique role by linking the arms of innate and adaptive immunity. Thus, an improved understanding of the human correlate to the Th-17 subset may reveal new targets for pharmacotherapy against lung disorders that are characterized by aberrant innate responses in host defense.

Circulating Th17 cells frequency is associated with the disease progression in HBV infected patients

BACKGROUND AND AIMS

Th17 cells have been shown to mediate host defensive mechanisms in various infections, but their role in HBV infection in humans has not been well characterized. In this study, we analyzed the frequency and cytokines secretion of circulating Th17 cells in HBV infected patients with different statuses, and also evaluated the potential association of Th17 frequency with the levels of liver injury.

METHODS

The study population consisted of 133 subjects, including 40 mild chronic hepatitis B (CHB) patients, 37 severe CHB patients, 20 acute hepatitis B (AHB) patients and 36 healthy controls. The frequency of circulating Th17 cells were carried out by intracellular cytokine staining analysis and serum IL-10 levels were measured by ELISA.

RESULTS

Our data shown that AHB and severe CHB patients had a significant increase of Th17 cells frequency in peripheral blood compared with mild CHB patients and healthy control (both P < 0.05). The elevated prevalence of Th17 cells is positively associated with the increased serum ALT levels in severe CHB patients (r= 0.457, P= 0.004) but had no correlation with serum HBV DNA load. In addition, the serum IL-10 were negatively correlated with the frequency of Th17 cells in PBMC from patients with chronic HBV infection (r=-0.452, P < 0.01).

CONCLUSION

Th17 cells may contribute to the disease progression and pathogenesis of liver injury in HBV infected patients, and the induction of IL-10 may be one mechanism of constraining pro-inflammatory Th17 responses.

Clinical outcome and IL-17, IL-23, IL-27 and FOXP3 expression in peripheral blood mononuclear cells of pollen-allergic children during sublingual immunotherapy

Induction of allergen-specific, tolerogenic, IL-10 and/or TGF-β-producing T-regulatory (Treg) cells that express transcription factor FOXP3 is considered as one of the key mechanisms of allergen-specific immunotherapy. However, little is known of the induction of FOXP3 expression in children during sublingual immunotherapy (SLIT). Recently, also, a novel subgroup of T-helper (Th) cells, the Th17 cells, secreting predominantly IL-17 (IL-17A), was identified. The expressions of IL-17 or the Th17-regulating cytokines IL-23 and IL-27 during SLIT are currently completely unexplored. This randomized, placebo-controlled dose-response study was performed to analyze the effects of SLIT on FOXP3, IL-17, IL-23, and IL-27 expressions in peripheral blood mononuclear cells (PBMC) of children with allergic rhinitis and their associations with clinical outcome. Thirty children were included: ten received SLIT with a glycerinated mixture of birch, hazel and alder with a cumulative weekly dose of 24,000 SQ-U, 10 with dose 200,000 SQ-U/wk, and ten received placebo. Cytokine and FOXP3 mRNA expressions in allergen-, purified protein derivative-stimulated and non-stimulated PBMC were determined at 0, 1 and 2 yr of SLIT by real-time RT-PCR (TaqMan). Symptoms and medications were recorded using diary cards. Allergen-induced IL-17 mRNA expression was significantly increased in the study subjects with elevated combined Symptom Medication Score (SMS) after 2 yr. There was also a significant positive correlation between the allergen-induced IL-17 and SMS in whole study group (r = 0.38, p = 0.039) and especially the 200,000 SQ-U dose-treated group (r = 0.74, p = 0.027) at 2 yr. Allergen-induced FOXP3 mRNA expression was significantly increased in the 200,000 SQ-U dose-treated children after two study years as compared with baseline (p = 0.016) and placebo-treated children (p = 0.028). The changes in FOXP3 mRNA expression positively correlated with IL-10 and TGF-β mRNAs during SLIT in whole study population. Increased allergen-induced IL-17 responses during SLIT are associated with elevated SMS. Increased tolerogenic, allergen-specific Treg responses are also observed in children during SLIT.

Interleukin-17 regulates chemokine and gelatinase B expression in fibroblasts to recruit both neutrophils and monocytes

Interleukin 17 (IL-17) is a proinflammatory cytokine, produced only by activated lymphocytes, but with a broad cellular host range. The effects of IL-17 on fibroblasts were investigated by analysis of the induction of chemokine and matrix metalloprotease (MMP) mRNA levels by RT-PCR. IL-17 stimulated CC chemokine (monocyte chemotactic protein-1; MCP-1/JE) and CXC (KC, MIP-2) chemokine and TIMP-1 mRNA expression in fibroblastoid L929 cells. In normal mouse embryonic fibroblasts (MEF) this induction profile by IL-17 was extended with the mRNAs encoding the chemokine granulocyte chemotactic protein-2 (GCP-2) and the proteases MMP-3, MMP-9 and MMP-13. The MMP-9 and GCP-2 induction by IL-17 in MEF, and the absence of induction in L929 cells, were corroborated by gelatin zymography and ELISA, respectively. The induction of MCP-1/CCL2 by IL-17 was confirmed in human diploid fibroblasts. We conclude that IL-17 regulates differentially chemokine and MMP expression by normal and transformed fibroblasts and is indirectly capable of attracting both monocytes and neutrophils to the inflammatory focus.

IL-17 stimulates the proliferation and differentiation of human mesenchymal stem cells: implications for bone remodeling

Interleukin-17 (IL-17) is a cytokine secreted primarily by T(H)-17 cells. Although IL-17 is primarily associated with the induction of tissue inflammation, the other biological roles of IL-17, including non-immune functions, have yet to be thoroughly explored. Here, we report that T-cell-produced IL-17 can induce proliferation of human bone marrow-derived mesenchymal stem cells (hMSCs) in a manner dependent on the generation of reactive oxygen species (ROS). Rac1 GTPase and NADPH oxidase 1 (Nox1) are activated by IL-17 to produce ROS, which in turn stimulates hMSC proliferation. The activation of the MEK-ERK pathway is also crucial for IL-17-dependent hMSC proliferation. TRAF6 and Act1 are required to activate Nox 1 and to phosphorylate MEK on IL-17 stimulation. Interestingly, IL-17 not only accelerates the proliferation of hMSCs, but also induces their migration, motility, and osteoblastic differentiation. Furthermore, IL-17 induces the expression of M-CSF and receptor activator of NF-kappaB ligand (RANKL) on hMSCs, thereby supporting osteoclastogenesis both in vivo and in vitro. On the basis of these results, we suggest that IL-17 can function as a signal to induce extensive bone turnover by regulating hMSC recruitment, proliferation, motility, and differentiation.

The IL-23/Th17 axis in the immunopathogenesis of psoriasis

Abnormal production of inflammatory mediators is believed to play an important role in the pathogenesis of psoriasis. Emerging data, both in mice and in humans, put the spotlight on a new subset of T helper (Th) cells, in part characterized by their production of IL-17 and accordingly named Th17 cells. Here, we review the development, characterization, and function of human Th17 cells as well as the crucial role of IL-23 in the context of Th17-cell-dependent chronic inflammation in psoriasis. We further discuss recent clinical trials targeting the IL-23/Th17 axis in psoriasis.

Induction, function and regulation of IL-17-producing T cells

Recent reports have provided convincing evidence that IL-17-producing T cells play a key role in the pathogenesis of organ-specific autoimmune diseases, a function previously attributed exclusively to IFN-gamma-secreting Th1 cells. Furthermore, it appears that IL-17-producing T cells can also function with Th1 cells to mediate protective immunity to pathogens. Although much of the focus has been on IL-17-secreting CD4+ T cells, termed Th17 cells, CD8+ T cells, gammadelta T cells and NKT cells are also capable of secreting IL-17. The differentiation of Th17 cells from naïve T cells appears to involve signals from TGF-beta, IL-6, IL-21, IL-1beta and IL-23. Furthermore, IL-1alpha or IL-1beta in synergy with IL-23 can promote IL-17 secretion from memory T cells. The induction or function of Th17 cells is regulated by cytokines secreted by the other major subtypes of T cells, including IFN-gamma, IL-4, IL-10 and at high concentrations, TGF-beta. The main function of IL-17-secreting T cells is to mediate inflammation, by stimulating production of inflammatory cytokines, such as TNF-alpha, IL-1beta and IL-6, and inflammatory chemokines that promote the recruitment of neutrophils and macrophages.

Identification of IL-18 and Th17 cells in salivary glands of patients with Sjögren's syndrome, and amplification of IL-17-mediated secretion of inflammatory cytokines from salivary gland cells by IL-18

IL-18 is a proinflammatory cytokine and plays an important pathogenic role in inflammatory and autoimmune disorders. IL-17 is also a proinflammatory cytokine and IL-17-secreting Th17 cells are involved in autoimmunity. However, the pathological roles of IL-18 and Th17 cells in Sjögren's syndrome (SS) remain to be elucidated. This study showed that the expression of IL-18 was detected in acinar cells, intraducts, and CD68(+) macrophages in salivary glands of SS patients, but not in those of healthy subjects or patients with chronic graft-vs-host disease, by immunohistochemistry, and immunoblot analysis revealed that 24-kDa precursor form of IL-18 (proIL-18) and 18-kDa mature IL-18 were detected in SS salivary glands. The majority of the infiltrating cells in the salivary glands of SS patients were CD4(+) T cells, and CD8(+) T cells were infiltrated to a lesser extent. The predominant expression of IL-17 was found in infiltrating CD4(+) T cells, whereas a small number of infiltrating CD8(+) T cells expressed IL-17. Human salivary gland HSY and acinar AZA3 cells constitutively expressed proIL-18 and caspase-1, and a calcium ionophore A23187 induced the secretion of IL-18 from the cells. HSY and AZA3 cells expressed IL-18R and IL-17R on the cell surface, and IL-18 amplified the secretion of IL-6 and IL-8 that were induced by low amounts of IL-17. Primary salivary gland cells from normal subjects partially confirmed these findings. These results suggest that IL-18 and Th17 cells detected in the salivary glands in SS patients are associated with the pathogenesis of SS in the salivary glands.