IL-25 regulates Th17 function in autoimmune inflammation

Biology of Interleukin-17 and Its Pathophysiological Significance in Sepsis

The interleukin (IL)-17 family includes six structure-related cytokines (A-F). To date, majority of studies have focused on IL-17A. IL-17A plays a pivotal role in various infectious diseases, inflammatory and autoimmune disorders, and cancer. Several recent studies have indicated that IL-17A is a biomarker as well as a therapeutic target in sepsis. In the current review, we summarize the biological functions of IL-17, including IL-17-mediated responses and signal transduction pathways, with particular emphasis on clinical relevance to sepsis.

T helper 17 cell-related cytokines in serum and saliva during management of periodontitis

AIM

T helper (Th)17 cells are implicated in the pathogenesis of periodontitis. This study investigated the effect of periodontal management on fifteen Th17-related cytokines in serum and saliva in periodontitis patients.

MATERIALS AND METHODS

Periodontal parameters, serum and saliva were collected from 40 healthy controls and 54 periodontitis subjects before treatment, and 3-, 6- and 12-months post-treatment. Cytokine concentrations of IL-1β, IL-4, IL-6, IL-10, IL-17A, IL-17F, IL-21, IL-22, IL-23, IL-25, IL-31, IL-33, IFN-γ, sCD40L and TNF-α were determined by Luminex assay.

RESULTS

IL-1β, IL-6, sCD40L and TNF-α in serum, and IL-1β, IL-6, IL-25 and IL-31 in saliva were significantly higher at baseline compared to health and decreased with treatment. In contrast, serum IL-31 was significantly lower at baseline compared to health and increased with treatment. In addition, salivary IL-10, IL-17A, IL-17F, IL-23, IL-33, IFN-γ and TNF-α also displayed treatment-related reduction. Correlation networks showed that cytokines in saliva displayed a higher number of correlations compared to serum in periodontitis.

CONCLUSION

Treatment generally decreased cytokine concentrations except for serum IL-31 which showed a treatment-related increase. Serum cytokine concentrations may not be reflective of salivary cytokines. Saliva may be a better medium for cytokine detection compared to serum. Serum IL-31 and salivary IL-1β, IL-6, IL-10 and TNF-α were significant predictors for mean probing depth and may be potential biomarkers of interest in the pathogenesis of periodontitis.

Ileal proteomic changes associated with IL-25-mediated resistance against intestinal trematode infections

Background

Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode, which has been extensively used to investigate the factors that determine the rejection of intestinal helminths. In this sense, several studies have shown that IL-25 is critical for the development of resistance against E. caproni in mice. In fact, treatment of mice with recombinant IL-25 generates resistance against primary E. caproni infection. However, the mechanisms by which IL-25 induces resistance remain unknown.

Methods

To study the mechanisms responsible for resistance elicited by IL-25, we analyzed the ileal proteomic changes induced by IL-25 in mice and their potential role in resistance. To this purpose, we compared the protein expression profiles in the ileum of four experimental groups of mice: naïve controls; E. caproni-infected mice; rIL-25-treated mice; and rIL-25-treated mice exposed to E. caproni metacercariae.

Results

Quantitative comparison by 2D-DIGE showed significant changes in a total of 41 spots. Of these, 40 validated protein spots were identified by mass spectrometry corresponding to 24 proteins.

Conclusions

Our results indicate that resistance to infection is associated with the maintenance of the intestinal epithelial homeostasis and the regulation of proliferation and cell death. These results provide new insights into the proteins involved in the regulation of tissue homeostasis after intestinal infection and its transcendence in resistance.

The role of interleukin-17 in asthma: a protective response?

While there now exist effective treatments for type 2 high, eosinophilic asthma, there are no specific therapies for 40–50% of people with asthma with other phenotypes, which result from poorly understood underlying pathological mechanisms. One such pathology is neutrophilic inflammation, which has been associated with interleukin (IL)-17 family cytokines. Human genetic studies identified IL-17 polymorphisms associated with asthma; in murine models of allergic airways disease, IL-17A contributes to airway hyperresponsiveness, and in humans, elevated airway IL-17A levels are repeatedly observed in severe asthma. However, the directionality of this association is unknown, and the assumption that IL-17 cytokines drive disease pathology remains speculative. Here, we explore the evidence underlying the relationship between IL-17 and asthma, we review lessons learned from investigating IL-17 in other inflammatory diseases, and discuss the possibility that IL-17 may even be protective in asthma rather than pathogenic. We also critically examine the newly proposed paradigm of a reciprocal relationship between type 2 and type 17 airways inflammation. In summary, we suggest an association between IL-17 and asthma, but research is needed examining the diverse functions of these cytokines, their longitudinal stability, their response to clinical interventions, and for mechanistic studies determining whether they are protective or pathogenic.

IL-17 cytokines have been implicated in neutrophilic asthma by genetic, murine and human data. Here, previous studies are critiqued and the assumption their dominant role is pathogenic rather than protective of airway epithelial barrier integrity is challenged.http://bit.ly/3axB4Zs

IL-25 exacerbates autoimmune aortitis in IL-1 receptor antagonist-deficient mice

IL-25, a member of the IL-17 family of cytokines, is known to enhance type 2 immune responses, but suppress type 3 (IL-17A)-mediated immune responses. Mice deficient in IL-1 receptor antagonist (Il1rn^−/− mice) have excessive IL-1 signaling, resulting in spontaneous development of IL-1–, TNF– and IL-17A–dependent aortitis. We found that expression of II25 mRNA was increased in the aortae of Il1rn^−/− mice, suggesting that IL-25 may suppress development of IL-1–, TNF– and IL-17A–dependent aortitis in Il1rn^−/− mice by inhibiting type 3-mediated immune responses. However, we unexpectedly found that Il25^−/−Il1rn^−/− mice showed attenuated development of aortitis, accompanied by reduced accumulation of inflammatory cells such as dendritic cells, macrophages and neutrophils and reduced mRNA expression of Il17a and Tnfa—but not Il4 or Il13—in local lesions compared with Il1rn^−/− mice. Tissue–, but not immune cell–, derived IL-25 was crucial for development of aortitis. IL-25 enhanced IL-1β and TNF production by IL-25 receptor–expressing dendritic cells and macrophages, respectively, at inflammatory sites of aortae of Il1rn^−/− mice, contributing to exacerbation of development of IL-1–, TNF– and IL-17A–dependent aortitis in those mice. Our findings suggest that neutralization of IL-25 may be a potential therapeutic target for aortitis.

Interleukin-17: Potential Target for Chronic Wounds

Chronic wounds exhibit persistent inflammation with markedly delayed healing. The significant burden of chronic wounds, which are often resistant to standard therapy, prompts further research on novel therapies. Since the interleukin-17 family has been implicated as a group of proinflammatory cytokines in immune-mediated diseases in the gut and connective tissue, as well as inflammatory skin conditions, we consider here if it may contribute to the pathogenesis of chronic wounds. In this review, we discuss the interleukin-17 family's signaling pathways and role in tissue repair. A PubMed review of the English literature on interleukin-17, wound healing, chronic wounds, and inflammatory skin conditions was conducted. Interleukin-17 family signaling is reviewed in the context of tissue repair, and preclinical and clinical studies examining its role in the skin and other organ systems are critically reviewed. The published work supports a pathologic role for interleukin-17 family members in chronic wounds, though this needs to be more conclusively proven. Clinical studies using monoclonal interleukin-17 antibodies to improve healing of chronic skin wounds have not yet been performed, and only a few studies have examined interleukin-17 family expression in chronic skin wounds. Furthermore, different interleukin-17 family members could be playing selective roles in the repair process. These studies suggest a therapeutic role for targeting interleukin-17A to promote wound healing; therefore, interleukin-17A may be a target worthy of pursuing in the near future.

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.

Akt3-Mediated Protection Against Inflammatory Demyelinating Disease

Akt is a serine/threonine protein kinase that plays a major role in regulating multiple cellular processes. While the isoforms Akt1 and Akt2 are involved in apoptosis and insulin signaling, respectively, the role for Akt3 remains uncertain. Akt3 is predominantly expressed in the brain, and total deletion of Akt3 in mice results in a reduction in brain size and neurodegeneration following injury. Previously, we found that Akt3-/- mice have a significantly worse clinical course during myelin-oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), an animal model in which autoreactive immune cells enter the CNS, resulting in inflammation, demyelination, and axonal injury. Spinal cords of Akt3-/- mice are severely demyelinated and have increased inflammation compared to WT, suggesting a neuroprotective role for Akt3 during EAE. To specifically address the role of Akt3 in neuroinflammation and maintaining neuronal integrity, we used several mouse strains with different manipulations to Akt3. During EAE, Akt3 Nmf350 mice (with enhanced Akt3 kinase activity) had lower clinical scores, a lag in disease onset, a delay in the influx of inflammatory cells into the CNS, and less axonal damage compared to WT mice. A significant increased efficiency of differentiation toward FOXP3 expressing iTregs was also observed in Akt3 Nmf350 mice relative to WT. Mice with a conditional deletion of Akt3 in CD4+ T-cells had an earlier onset of EAE symptoms, increased inflammation in the spinal cord and brain, and had fewer FOXP3+ cells and FOXP3 mRNA expression. No difference in EAE outcome was observed when Akt3 expression was deleted in neurons (Syn1-CKO). These results indicate that Akt3 signaling in T-cells and not neurons is necessary for maintaining CNS integrity during an inflammatory demyelinating disease.

Systemic effects of IL-17 in inflammatory arthritis

Inflammatory arthritis occurs in many diseases and is characterized by joint inflammation and damage. However, the inflammatory state in arthritis is commonly associated with systemic manifestations, which are generally linked to a poor prognosis. The pro-inflammatory cytokine IL-17 functions within a complex network of cytokines and contributes to the pathogenesis of various inflammatory diseases. Three IL-17 inhibitors have already been approved for the treatment of psoriasis, psoriatic arthritis, and ankylosing spondylitis. After a brief description of IL-17 and its local effects on joints, this Review focuses on the systemic effects of IL-17 in inflammatory arthritis. Increased circulating concentrations of bioactive IL-17 mediate changes in blood vessels, liver and cardiac and skeletal muscles. The effects of IL-17 on vascular and cardiac cells might contribute to the increased risk of cardiovascular events that occurs in all patients with inflammatory disorders. In the liver, IL-17 contributes to the high circulating concentrations of acute-phase proteins, such as C-reactive protein, and the appearance of liver lesions. In skeletal muscle, IL-17 contributes to muscle contractibility defects and weakness. Thus, targeting IL-17 might have beneficial effects at both local and systemic levels, and could also be proposed for the treatment of a wider range of inflammatory diseases.

Interleukin-25 is upregulated in patients with systemic lupus erythematosus and ameliorates murine lupus by inhibiting inflammatory cytokine production

Interleukin-25 (IL-25), an anti-inflammatory member of the IL-17 family of cytokines, has been extensively investigated in multiple autoimmune and inflammatory diseases. However, its pathogenic role in systemic lupus erythematosus (SLE) remains largely unknown. This study aimed to explore the expression and clinical significance of IL-25 in patients with SLE as well as its pathogenic role in lupus-prone MRL/lpr mice. The results showed that IL-25 mRNA and serum levels were increased in patients with SLE compared with those in healthy controls. Higher IL-25 mRNA and serum levels were found in patients with an active disease. IL-25 levels were positively associated with SLEDAI, anti-dsDNA, and IgG but negatively associated with C3 and C4. Ex vivo assay showed that IL-25 could inhibit the production of the inflammatory cytokines IL-1β, IL-17, IL-6, and IFN-γ as well as TNF-α in the peripheral blood mononuclear cells in patients with SLE. In vivo studies revealed that treatment with IL-25 significantly ameliorated lupus symptoms in lupus-prone MRL/lpr mice by suppressing the production of inflammatory cytokines, including IL-1α, IL-1β, IL-6, IL-12p70, IL-17A, and IFN-β. Cumulatively, our results suggest that IL-25 levels are increased in patients with SLE and associated with disease activity; IL-25 plays a potent immunosuppressive role in the pathogenesis of SLE by suppressing the production of inflammatory cytokines. IL-25 could potentially be used as a diagnostic and therapeutic target for SLE treatment.

Dendritic Cell-Mediated Th2 Immunity and Immune Disorders

Dendritic cells (DCs) are the professional antigen-presenting cells that recognize and present antigens to naïve T cells to induce antigen-specific adaptive immunity. Among the T-cell subsets, T helper type 2 (Th2) cells produce the humoral immune responses required for protection against helminthic disease by activating B cells. DCs induce a Th2 immune response at a certain immune environment. Basophil, eosinophil, mast cells, and type 2 innate lymphoid cells also induce Th2 immunity. However, in the case of DCs, controversy remains regarding which subsets of DCs induce Th2 immunity, which genes in DCs are directly or indirectly involved in inducing Th2 immunity, and the detailed mechanisms underlying induction, regulation, or maintenance of the DC-mediated Th2 immunity against allergic environments and parasite infection. A recent study has shown that a genetic defect in DCs causes an enhanced Th2 immunity leading to severe atopic dermatitis. We summarize the Th2 immune-inducing DC subsets, the genetic and environmental factors involved in DC-mediated Th2 immunity, and current therapeutic approaches for Th2-mediated immune disorders. This review is to provide an improved understanding of DC-mediated Th2 immunity and Th1/Th2 immune balancing, leading to control over their adverse consequences.

[New protagonists in asthma pathophysiology]

Asthma is often associated with a Th2-type immune response with well-known cellular and molecular actors such as eosinophils, Th2 lymphocytes and associated cytokines such as interleukin-5 or IL-4. Nevertheless, some of the asthmatic patients show clinical manifestations and characteristics that do not correspond to the current pattern of the pathophysiology of asthma. Thus, recently new cellular and molecular actors in the development of asthma have been demonstrated in animal models and in humans. Among these are components of the innate immune system such as type 2 innate lymphoid cells or adaptive immune system such as Th9 lymphocytes. At the cellular level, the role of small G proteins in asthma is also highlighted as well as the role of major cytokines like IL-17 or those derived from the epithelium. A better knowledge of the physiopathology of asthma and the taking into account of these new actors allows the identification of new therapeutic targets for different endotypes of patients.

IL-17 in Rheumatoid Arthritis and Precision Medicine: From Synovitis Expression to Circulating Bioactive Levels

Interleukin (IL)-17A has a direct contribution in early induction and late chronic stages of various inflammatory diseases. In vitro and in vivo experiments have first characterized its local effects on different cell types and then its systemic effects. For instance, IL-17 axis is now identified as a key driver of psoriasis through its effects on keratinocytes. Similar observations apply for rheumatoid arthritis (RA) where IL-17A triggers changes in the synovium that lead to synovitis and maintain local inflammation. These results have prompted the development of biologics to target this cytokine. However, while convincing studies are reported on the efficacy of IL-17 inhibitors in psoriasis, there are conflicting results in RA. Patient heterogeneity but also the involvement of mediators that regulate IL-17 function may explain these results. Therefore, new tools and concepts are required to identify patients that could benefit from these IL-17 targeted therapies in RA and the development of predictive biomarkers of response has started with the emergence of various bioassays. Current strategies are also focusing on synovial biopsies that may be used to stratify patients. From local to systemic levels, new approaches are developing and move the field of RA management into the era of precision medicine.

The Interleukin-17 Family of Cytokines in Breast Cancer

Breast cancer (BC) is the most common cancer in women worldwide and remains a major cause of mortality with an expected 137,000 death this year in Europe. Standard management of metastatic BC comprises hormonotherapy, chemotherapy, and targeted therapies. Cyclin dependent kinase (CDK) and mammalian target of rapamycin (mTOR) inhibitors have recently proved their efficiency in hormonal receptor expressing BC. Checkpoint proteins inhibition is being evaluated in phase 3 studies. Since inflammation is constantly present in cancers, research teams have focused their attention on the interleukin-17 (IL-17) family of proinflammatory cytokines. Preclinical experiments have reported both pro and antitumor effects depending on the conditions. In the present article, we review the accumulating evidences about the roles of IL-17 in BC and discuss whether this family of cytokines could be a new target in anticancer treatments.

Biological Properties and the Role of IL-25 in Disease Pathogenesis

The interleukin- (IL-) 17 superfamily, a T cell-derived cytokine, consists of 6 ligands (IL-17A-IL-17F) and 5 receptors (IL-17RA-IL-17RE). IL-17A, a prototype member of this family, is involved in the pathogenesis of allergies, autoimmune diseases, allograft transplantations, and malignancies. By contrast, IL-17B is reported to be closely related to certain diseases, particularly tumors such as breast cancer, gastric cancer, and pancreatic cancer. Recently, the biological function of IL-17E (also called IL-25) in disease, particularly airway diseases, has attracted the attention of researchers. However, studies on IL-25 are scant. In this review, we detail the structural characteristics, expression patterns, responder cells, biological properties, and role of IL-25 in disease pathogenesis.

Concerted IL-25R and IL-4Rα signaling drive innate type 2 effector immunity for optimal helminth expulsion

Interleukin 25 (IL-25) is a major 'alarmin' cytokine, capable of initiating and amplifying the type immune response to helminth parasites. However, its role in the later effector phase of clearing chronic infection remains unclear. The helminth Heligmosomoides polygyrus establishes long-term infections in susceptible C57BL/6 mice, but is slowly expelled in BALB/c mice from day 14 onwards. We noted that IL-25R (Il17rb)-deficient BALB/c mice were unable to expel parasites despite type 2 immune activation comparable to the wild-type. We then established that in C57BL/6 mice, IL-25 adminstered late in infection (days 14-17) drove immunity. Moreover, when IL-25 and IL-4 were delivered to Rag1-deficient mice, the combination resulted in near complete expulsion of the parasite, even following administration of an anti-CD90 antibody to deplete innate lymphoid cells (ILCs). Hence, effective anti-helminth immunity during chronic infection requires an innate effector cell population that is synergistically activated by the combination of IL-4Rα and IL-25R signaling.

The IL-17 Family of Cytokines in Psoriasis: IL-17A and Beyond

Psoriasis is a frequent chronic inflammatory skin disease, nowadays considered a major global health problem. Several new drugs, targeting the IL-23/IL-17A pathway, have been recently licensed or are in clinical development. These therapies represent a major improvement of the way in which psoriasis is managed, since they show an unprecedented efficacy on skin symptoms of psoriasis. This has been made possible, thanks to an increasingly more accurate pathogenic view of psoriasis. Today, the belief that Th17 cells mediate psoriasis is moving to the concept of psoriasis as an IL-17A-driven disease. New questions arise at the horizon, given that IL-17A is part of a newly described family of cytokines, which has five distinct homologous: IL-17B, IL-17C, IL-17D, IL-17E, also known as IL-25 and IL-17F. IL-17 family cytokines elicit similar effects in target cells, but simultaneously trigger different and sometimes opposite functions in a tissue-specific manner. This is complicated by the fact that IL-17 cytokines show a high capacity of synergisms with other inflammatory stimuli. In this review, we will summarize the current knowledge around the cytokines belonging to the IL-17 family in relation to skin inflammation in general and psoriasis in particular, and discuss possible clinical implications. A comprehensive understanding of the different roles played by the IL-17 cytokines is crucial to appreciate current and developing therapies and to allow an effective pathogenesis- and mechanisms-driven drug design.

The flavonoid kurarinone inhibits clinical progression of EAE through inhibiting Th1 and Th17 cell differentiation and proliferation

INTRODUCTION

The flavonoid kurarinone suppresses CD4+ T-cell-mediated chronic inflammatory dermatitis. However, kurarinone's effects upon autoimmune central nervous system (CNS) disease remain unknown. We investigated the potential therapeutic effects and molecular mechanism(s) of kurarinone in an experimental autoimmune encephalomyelitis (EAE) murine model of multiple sclerosis (MS).

MATERIALS AND METHODS

Myelin oligodendrocyte glycoprotein (MOG_35-55) peptide-induced EAE was constructed in wild-type mice. Effects of kurarinone (100 mg/kg/day) upon clinical scores were assessed based on physical traits and signs. Spinal cord sections were extracted to assess inflammation, demyelination, and mRNA expression of key pro-inflammatory cytokines and chemokines. CNS-infiltrating mononuclear cells (MNCs) and splenocytes were harvested; flow cytometry was then applied to determine CD4+ and CD8+ T-cell percentages as well as Th1/Th2/Th17 subset percentages. Purified naïve CD4+ T-cells underwent in vitro T-cell polarization and proliferation to assess kurarinone's effects.

RESULTS

Prophylactic and treatment regimens of kurarinone significantly improved clinical scores in the MOG_35-55 peptide-induced EAE model (P < 0.05). Kurarinone significantly lowered CNS inflammation and demyelination (61% and 83% decreases, respectively; P < 0.05), significantly decreased MNC infiltration into CNS tissue (42% decrease; P < 0.05), and significantly inhibited levels of several pro-inflammatory cytokines and chemokines (P < 0.05). Kurarinone significantly lowered CD4+ and CD8+ CNS T-cell counts (51% and 80% decreases, respectively; P < 0.05) and significantly reduced CNS Th1 and Th17 cell percentages (24% and 44% decreases, respectively; P < 0.05). Kurarinone significantly inhibited in vitro Th1, Th2, and Th17 cell differentiation and proliferation (P < 0.05).

CONCLUSIONS

Kurarinone significantly inhibits the clinical progression of EAE through the inhibition of Th1 and Th17 cell differentiation and proliferation. Kurarinone may show promise as an immunomodulatory therapeutic agent in treating MS.

Deep Resequencing of Ulcerative Colitis-Associated Genes Identifies Novel Variants in Candidate Genes in the Korean Population

BACKGROUND

Genome-wide association studies and meta-analyses have revealed the genetic background of ulcerative colitis (UC) by identifying common variants. However, these variants do not fully explain the disease variance in UC. To identify novel variants, we performed deep resequencing of UC-associated genes in Korean UC patients and subsequently investigated the functional roles of identified susceptibility genes.

METHODS

We performed targeted deep resequencing of 108 genes in 24 Korean UC patients and then performed association analysis with data from 126 healthy controls. We validated these variants using 2-stage replication studies including 793 UC patients and 783 controls. We performed in silico and pathway analyses and functional analyses.

RESULTS

The combined analysis including 2 replication studies identified 6 novel susceptibility loci and reconfirmed 10 previously reported loci. Among the novel single nucleotide variants (SNVs), rs10035653 in C5orf55 (P = 2.08 × 10-3; OR = 1.50), rs41417449 in BTNL2 (P = 1.27 × 10-2; OR = 1.32), rs3117099 in HCG23 (P = 9.98 × 10-6; OR = 1.40), rs7192 in HLA-DRA (P = 6.95 × 10-9; OR = 1.57), and rs3744246 in ORMDL3 (P = 2.21 × 10-2; OR = 1.21) were identified as causal variants, whereas rs713669 in IL17REL (P = 2.69 × 10-2; OR = 0.84) as a protective variant for UC. When correcting multiple testing, 3 novel SNVs (rs41417449 in BTNL2, rs3744246 in ORMDL3, and rs713669 in IL17REL) and 4 previously reported SNVs did not reach a statistical significance. Functional study suggested that SNVs of BTNL2 and C5orf55 exacerbated the inflammatory response both in vitro and in vivo.

CONCLUSIONS

This study identified 3 novel susceptibility loci and validated 6 previously reported SNVs for UC through deep resequencing in Koreans and revealed the functional roles of BTNL2 and C5orf55.

Interleukin-25 reduces Th17 cells and inflammatory responses in human peripheral blood mononuclear cells

BACKGROUND

The absence of interleukin-25 (IL-25) favors the induction of Th1 and Th17 immune responses in mice. Th1 immune responses have been associated with the pathology of atherosclerosis, a lipid and inflammation driven disease of the arterial wall.

PURPOSE OF RESEARCH

To evaluate the effect of IL-25 on human peripheral blood mononuclear cells (hPBMCs) in the presence and absence of oxidized low density lipoprotein (oxLDL), a key player in atherosclerosis development.

PRINCIPAL RESULTS

Human PBMCs were incubated with recombinant human IL-25 (rhIL-25) in the presence and absence of oxLDL and analyzed with flow cytometry while cytokine secretion was measured in cell culture supernatants. The IL-25 receptor, IL-17RB, was mostly expressed on T cells. Incubation of hPBMCs with IL-25 reduced the frequency of Th17 cells. Furthermore, IL-25 inhibited the release of the Th17-inducing cytokine IL-6 from dendritic cells isolated from hPBMCs indicating that the IL-25 mediated Th17 suppression may be indirect. Moreover, IL-25 reduced the secretion of the proinflammatory cytokine IFNγ from hPBMCs. OxLDL decreased IFNγ release from hPBMCs regardless of the presence or absence of IL-25.

CONCLUSIONS

IL-25 reduces Th1 and Th17 immune responses in hPBMCs raising the interesting possibility that IL-25 could have a protective role in human atherosclerosis.

Interleukin-25 Axis Is Involved in the Pathogenesis of Human Primary and Experimental Murine Sjögren's Syndrome

OBJECTIVE

To investigate the role of the interleukin-25 (IL-25)/IL-17 receptor B (IL-17RB) axis in experimental Sjögren's syndrome (SS) and in patients with primary SS and primary SS-associated lymphoma.

METHODS

Expression of IL-25, IL-17RB, IL-17B, and tumor necrosis factor receptor-associated factor 6 (TRAF6) was analyzed on minor salivary gland (SG) samples from patients with primary SS and on parotid gland samples from patients with primary SS-associated B cell non-Hodgkin's lymphoma (NHL). IL-17RB expression and the frequencies of natural group 2 innate lymphoid cells (ILC2s), inflammatory ILC2s, and M2-polarized macrophages were assessed by flow cytometry in SG mononuclear cells and peripheral blood mononuclear cells (PBMCs). Tissue distribution of ILC2s was studied by confocal microscopy. The role of recombinant IL-25 and of rituximab in modulating IL-25 expression was investigated in in vitro studies. IL-25/IL-17RB and TRAF6 expression and the role of IL-25 inhibition were also studied in the experimental murine model of SS.

RESULTS

Activation of the IL-25/IL-17RB/TRAF6 axis correlated with the focus score and was observed in patients with primary SS and in patients with primary SS-associated NHL. A significant increase in the frequency of inflammatory ILC2s was observed both in SG mononuclear cells and in PBMCs. IL-25 stimulation of isolated SG mononuclear cells and PBMCs from patients and controls resulted both in inflammatory ILC2 expansion and in increased autoantibody production. Rituximab modulated expression of inflammatory ILC2s and IL-25 in primary SS. SG protein-immunized mice developed overt SS symptoms with increased IL-25 expression and increased frequency of CD4+IL-17RB+TRAF6+ cells. IL-25 neutralization attenuated disease progression and tissue pathology in mice with experimental SS.

CONCLUSION

IL-25 may promote the inflammatory state in primary SS and may be a potential target for novel disease-modifying therapeutic strategies in patients with primary SS.

Interleukin 17 Family Cytokines: Signaling Mechanisms, Biological Activities, and Therapeutic Implications

The cytokines of the interleukin 17 (IL-17) family play a central role in the control of infections, especially extracellular fungi. Conversely, if unrestrained, these inflammatory cytokines contribute to the pathology of numerous autoimmune and chronic inflammatory conditions. Recent advances have led to the approval of IL-17A-blocking biologics for the treatment of moderate to severe plaque psoriasis, but much remains to be understood about the biological functions, regulation, and signaling pathways downstream of these factors. In this review, we outline the current knowledge of signal transduction and known physiological activities of IL-17 family cytokines. We will highlight in particular the current understanding of these cytokines in the context of skin manifestations of disease.

IL-25 in allergic inflammation

IL-25, also known as IL-17E, is a member of the IL-17 cytokine family mostly produced by epithelial cells and innate immune cells. After binding to the IL-17RB/IL-17RA complex, IL-25 induces downstream signaling responses in epithelial cells and type 2 lymphocytes, which initiates, propagates, and sustains type 2 immunity. The function of IL-25 in allergic diseases such as asthma has been well established, and now also is extended to diseases such as inflammatory bowel disease and cancer. This review summarizes the literature on IL-25 and discusses the unsolved questions. Our knowledge on IL-25 will pave the pathway for targeting this cytokine in inflammatory diseases.

Interleukin-25 (IL-25) has a protective role in atherosclerosis development in the aortic arch in mice

Atherosclerosis is a chronic inflammatory disease characterized by the entrapment of apolipoprotein B-containing lipoproteins in the arterial intima, leading to local inflammation. T helper (Th) cell 1-mediated immune responses have been associated with atherosclerosis, and the cytokine interleukin-25 (IL-25 or IL-17E) has been reported to potentially regulate Th1 cell- and Th17 cell-related immune responses. In this study, we evaluated the effects of complete IL-25 deficiency or of a temporal IL-25 blockade on atherosclerosis development in apolipoprotein E-deficient (Apoe^-/-) mice. Mice deficient in both apolipoprotein E and IL-25 (Apoe^-/-/IL-25^-/-) had more Th1 cells in the spleen, along with elevated plasma levels of IL-17 and an increased release of splenic interferon-γ (INF-γ). In support of this observation, a 4-week-long treatment of young Apoe^-/- mice (at 10-14 weeks of age) with an IL-25-blocking antibody increased the release of Th1/Th17-associated cytokines in the spleen. In both mouse models, these findings were associated with increased atherosclerotic plaque formation in the aortic arch. We conclude that complete IL-25 deficiency and a temporal IL-25 blockade during early plaque development aggravate atherosclerosis development in the aortic arch of Apoe^-/- mice, accompanied by an increase in Th1/Th17-mediated immune responses. Our finding that endogenous IL-25 has an atheroprotective role in the murine aortic arch has potential implications for atherosclerosis development and management in humans.

IL-25 enhances TH17 cell-mediated contact dermatitis by promoting IL-1β production by dermal dendritic cells

BACKGROUND

In addition to thymic stromal lymphopoietin and IL-33, IL-25 is known to induce T_H2 cytokine production by various cell types, including T_H2 cells, T_H9 cells, invariant natural killer T cells, and group 2 innate lymphoid cells, involved in T_H2-type immune responses. Because both T_H2-type and T_H17-type cells/cytokines are crucial for contact hypersensitivity (CHS), IL-25 can contribute to this by enhancing T_H2-type immune responses. However, the precise role of IL-25 in the pathogenesis of fluorescein isothiocyanate-induced CHS is poorly understood.

OBJECTIVE

We investigated the contribution of IL-25 to CHS using Il25^-/- mice.

METHODS

CHS was evaluated by means of measurement of ear skin thickness in mice after fluorescein isothiocyanate painting. Skin dendritic cell (DC) migration, hapten-specific T_H cell differentiation, and detection of IL-1β-producing cells were determined by using flow cytometry, ELISA, and immunohistochemistry, respectively.

RESULTS

In contrast to thymic stromal lymphopoietin, we found that IL-25 was not essential for skin DC migration or hapten-specific T_H cell differentiation in the sensitization phase of CHS. Unexpectedly, mast cell- and non-immune cell-derived IL-25 was important for hapten-specific T_H17 cell-mediated rather than T_H2 cell-mediated inflammation in the elicitation phase of CHS by enhancing T_H17-related, but not T_H2-related, cytokines in the skin. In particular, IL-1β produced by dermal DCs in response to IL-25 was crucial for hapten-specific T_H17 cell activation, contributing to induction of local inflammation in the elicitation phase of CHS.

CONCLUSION

Our results identify a novel IL-25 inflammatory pathway involved in induction of T_H17 cell-mediated, but not T_H2 cell-mediated, CHS. IL-25 neutralization can be a potential approach for treatment of CHS.

High salt diet stimulates gut Th17 response and exacerbates TNBS-induced colitis in mice

This study focuses on characterizing the effect of a high salt diet (HSD) on intestinal immunity and the risk of inflammatory bowel diseases (IBD). We found that mice on a HSD had an increased frequency of IL-17A producing cells in the intestinal lamina propria (LP) compared to mice on a normal diet (ND). Furthermore, most intestinal IL-17A producing cells were CD4⁺TCRβ⁺ cells. A HSD increased the LP T helper 17 (Th17) responses in both the small and large intestines but did not increase the Th17 response of other gut-associated lymphoid organ. Although, HSD did not change the percentage of regulatory T (Treg) cells, HSD significantly inhibit secretion of IL-10 and the suppressive function of Treg cells. Moreover, we found that HSD exacerbates trinitrobenzenesulfonic acid (TNBS) induced colitis, and Th17 response was significantly increased in the colonic LP of HSD TNBS-treated mice compared with the ND TNBS-treated mice. This study demonstrates that HSD stimulates the intestinal Th17 response but inhibits the function of Treg cells. Moreover, HSD exacerbates TNBS induced mice colitis, suggesting that HSD disrupts the intestinal immunity and increases the risk of IBD.

Exome Sequencing Diagnoses X-Linked Moesin-Associated Immunodeficiency in a Primary Immunodeficiency Case

Background

We investigated the molecular etiology of a young male proband with confirmed immunodeficiency of unknown cause, presenting with recurrent bacterial and Varicella zoster viral infections in childhood and persistent lymphopenia into early adulthood.

Aim

To identify causative functional genetic variants related to an undiagnosed primary immunodeficiency.

Method

Whole genome microarray copy number variant (CNV) analysis was performed on the proband followed by whole exome sequencing (WES) and trio analysis of the proband and family members. A >4 kbp deletion identified by repeated CNV analysis of exome sequencing data along with three damaging missense single nucleotide variants were validated by Sanger sequencing in all family members. Confirmation of the causative role of the candidate gene was performed by qPCR and Western Blot analyses on the proband, family members and a healthy control.

Results

CNV identified our previously reported interleukin 25 amplification in the proband; however, the variant was not validated to be a candidate gene for immunodeficiency. WES trio analysis, data filtering and in silico prediction identified a novel, damaging (SIFT: 0; Polyphen 1; Grantham score: 101) and disease-causing (MutationTaster) single base mutation in the X chromosome (c.511C > T p.Arg171Trp) MSN gene not identified in the UCSC Genome Browser database. The mutation was validated by Sanger sequencing, confirming the proband was hemizygous X-linked recessive (–/T) at this locus and inherited the affected T allele from his non-symptomatic carrier mother (C/T), with other family members (father, sister) confirmed to be wild type (C/C). Western Blot analysis demonstrated an absence of moesin protein in lymphocytes derived from the proband, compared with normal expression in lymphocytes derived from the healthy control, father and mother. qPCR identified significantly lower MSN mRNA transcript expression in the proband compared to an age- and sex-matched healthy control subject in whole blood (p = 0.02), and lymphocytes (p = 0.01). These results confirmed moesin deficiency in the proband, directly causative of his immunodeficient phenotype.

Conclusion

These findings confirm X-linked moesin-associated immunodeficiency in a proband previously undiagnosed up to 24 years of age. This study also highlights the utility of WES for the diagnosis of rare or novel forms of primary immunodeficiency disease.

Role of Th17 and Treg cells in septic arthritis and the impact of the Th17/Treg -derived cytokines in the pathogenesis of S. aureus induced septic arthritis in mice

Intravenous inoculation of Swiss mice with S. aureus leads to severe synovial joint tissue swelling along with prominent T lymphocyte infiltrate with associated inflammation in synovial tissue. Cytokines released from macrophages such as TNF-α, IL-1β and IL-6 the main players that precede cartilage and bone destruction during septic arthritis (SA) followed by osteoclast differentiation and bone resorption. CD4⁺ naïve T cells upon cytokine driven activation, differentiate into lineages of helper (Th) and regulatory T cells (Treg) including inflammatory Th17 cell lineage. Acting as counterbalance, Tregs protect the host by releasing anti-inflammatory IL-10. A disturbed balance between Th17 and Treg cell development skews the pathways towards Th17 lineage, but how it actually induces SA is still unexplored. Therefore, this study has been attempted to demonstrate the Th17/Treg ratio in synovial tissue, spleen and peripheral blood by FACS and their derived cytokines from serum of arthritic mice. Here, we reported that the ratios of Th17/Treg as well as their related cytokine levels were increased at 3 days post-infection which was decreased during 9 DPI but heightened again at 15DPI resulting in persistence of the disease, though decreased again at 30 DPI even in animals with increased dose of infection. Bacterial colonies were present in synovial joints at 15 DPI in animals with increased infection but found to be absent at 30 DPI. Maintaining Th17/Treg balance by neutralizing functionally active Th17 and their related cytokines or adoptive transfer of fully active Tregs and/or their related cytokines may lead to a novel therapeutic strategy for combating Staphylococcal arthritis.

Role of interleukin-25 in development of spontaneous arthritis in interleukin-1 receptor antagonist-deficient mice

Interleukin (IL)-25, which is a member of the IL-17 family of cytokines, induces production of such Th2 cytokines as IL-4, IL-5, IL-9 and/or IL-13 by various types of cells, including Th2 cells, Th9 cells and group 2 innate lymphoid cells (ILC2). On the other hand, IL-25 can suppress Th1- and Th17-associated immune responses by enhancing Th2-type immune responses. Supporting this, IL-25 is known to suppress development of experimental autoimmune encephalitis, which is an IL-17-mediated autoimmune disease in mice. However, the role of IL-25 in development of IL-17-mediated arthritis is not fully understood. Therefore, we investigated this using IL-1 receptor antagonist-deficient (IL-1Ra^-/-) mice, which spontaneously develop IL-17-dependent arthritis. However, development of spontaneous arthritis (incidence rate, disease severity, proliferation of synovial cells, infiltration of PMNs, and bone erosion in joints) and differentiation of Th17 cells in draining lymph nodes in IL-25^-/- IL-1Ra^-/- mice were similar to in control IL-25^+/+ IL-1Ra^-/- mice. These observations indicate that IL-25 does not exert any inhibitory and/or pathogenic effect on development of IL-17-mediated spontaneous arthritis in IL-1Ra^-/- mice.

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IL-25 is known to inhibit Th17 cell differentiation.

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IL-25 is known to suppress Th17-mediated autoimmune diseases in mice.

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IL-25 does not play any inhibitory and/or pathogenic role in IL-17-mediated arthritis.

Novel therapies for immune-mediated inflammatory diseases: What can we learn from their use in rheumatoid arthritis, spondyloarthritis, systemic lupus erythematosus, psoriasis, Crohn's disease and ulcerative colitis?

The past three decades have witnessed remarkable advances in our ability to target specific elements of the immune and inflammatory response, fuelled by advances in both biotechnology and disease knowledge. As well as providing superior treatments for immune-mediated inflammatory diseases (IMIDs), such therapies also offer unrivalled opportunities to study the underlying immunopathological basis of these conditions.In this review, we explore recent approaches to the treatment of IMIDs and the insights to pathobiology that they provide. We review novel biologic agents targeting the T-helper 17 axis, including therapies directed towards interleukin (IL)-17 (secukinumab, ixekizumab, bimekizumab), IL-17R (brodalumab), IL-12/23p40 (ustekinumab, briakinumab) and IL-23p19 (guselkumab, tildrakizumab, brazikumab, risankizumab, mirikizumab). We also present an overview of biologics active against type I and II interferons, including sifalumumab, rontalizumab, anifrolumab and fontolizumab. Emerging strategies to interfere with cellular adhesion processes involved in lymphocyte recruitment are discussed, including both integrin blockade (natalizumab, vedolizumab, etrolizumab) and sphingosine-1-phosphate receptor inhibition (fingolimod, ozanimod). We summarise the development and recent application of Janus kinase (JAK) inhibitors in the treatment of IMIDs, including first-generation pan-JAK inhibitors (tofacitinib, baricitinib, ruxolitinib, peficitinib) and second-generation selective JAK inhibitors (decernotinib, filgotinib, upadacitinib). New biologics targeting B-cells (including ocrelizumab, veltuzumab, tabalumab and atacicept) and the development of novel strategies for regulatory T-cell modulation (including low-dose IL-2 therapy and Tregitopes) are also discussed. Finally, we explore recent biotechnological advances such as the development of bispecific antibodies (ABT-122, COVA322), and their application to the treatment of IMIDs.

The signaling axis of microRNA-31/interleukin-25 regulates Th1/Th17-mediated inflammation response in colitis

Interleukin-25 (IL-25) is an important regulatory cytokine that has a key role on mucosal immune tolerance during inflammation response. However, the molecular mechanism that regulates the colonic IL-25 expression in Crohn's disease (CD) remains unclear. In this study, IL-25 level was proved to decrease in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis mice and IL-10 knockout (KO) spontaneous colitis mice. An inverse correlation between IL-25 and miR-31 was discovered in the colons from model mice and CD patients. Furthermore, target validation analysis demonstrated that miR-31 directly regulated IL-25 expression by binding to its messenger RNA 3'-untranslated region. Changing colonic miR-31 level in the colitis mice could affect the mucosal IL-12/23-mediated Th1/Th17 pathway and lead to either amelioration or aggravation of colonic inflammation. In addition, the therapeutic effects of anti-miR-31 in TNBS-induced colitis were abolished by colonic treatment with IL-25 antibody or colonic down-expression of IL-25. Our findings demonstrated that IL-25 could be a crucial anti-inflammatory cytokine in TNBS-induced colitis and the signaling of miR-31 targeting IL-25 might be a possible mechanism that regulates IL-12/23-mediated Th1/Th17 inflammatory responses during colonic inflammation process. Restoring colonic IL-25 expression and blocking Th1/Th17 responses via intracolonic administration of miR-31 inhibitor may represent a promising approach for CD treatment.

Interleukin-25 Produced by Synoviocytes Has Anti-inflammatory Effects by Acting As a Receptor Antagonist for Interleukin-17A Function

The production and function of cytokines are highly regulated. One mechanism is the balance between pro- and anti-inflammatory cytokines. As interleukin (IL)-17A and IL-25 share the IL-17RA receptor chain, we hypothesize that IL-25 acts as an IL-17A receptor antagonist and limits its pro-inflammatory effects. The production and expression kinetics of IL-25 and its receptor chains IL-17RA and RB were analyzed in rheumatoid synoviocytes alone or in coculture with peripheral blood mononuclear cells (PBMCs). The effects of autocrine or exogenous IL-25 on synoviocytes were investigated in the presence or not of an anti-IL-25 antibody. To study the regulatory effects of IL-25, synoviocytes and/or PBMCs were exposed to IL-25 before being treated with IL-17A and tumor necrosis factor alpha (TNF-α) alone or combined. IL-25, IL-6, and bioactive IL-17A were quantified in rheumatoid arthritis (RA) patient plasma. Synoviocytes expressed and secreted IL-25, and expressed the two chains of its receptor IL-17RA and IL-17RB. IL-17RB expression was increased by TNF-α. IL-25 production occurred at a delayed time point (5 days) after stimulation with IL-17A and TNF-α. Synoviocytes pretreated with IL-25 were less responsive to IL-17A and TNF-α. PBMCs exposed to IL-25 showed a decreased production of pro-inflammatory mediators, including IL-17A with a 57% decrease; p = 0.002. IL-25 levels were elevated in the plasma of RA patients compared to healthy subjects (p = 0.03). However, these levels are not high enough to inhibit the function of circulating IL-17A. In conclusion, it was shown for the first time that synoviocytes produce IL-25, specifically at late time points and that IL-25 acts as a regulator of IL-17A-driven inflammation, as indicated by in vitro results and in vivo, in a long-term RA patient follow-up. These results may be important when considering IL-17A inhibition.

Deletion of Shp2 in bronchial epithelial cells impairs IL-25 production in vitro, but has minor influence on asthmatic inflammation in vivo

Shp2 played an important role in cigarette-smoke-mediated inflammation, surfactant homeostasis and asthmatic airway remodeling. However, whether shp2 plays a key role in epithelium-associated allergic reaction is still unknown. In this study, LPS and OVA were observed to induce the production of IL-25 in bronchial epithelial cells in vitro via the activation of MAPK p38 and JNK. Furthermore, blockage of Shp2 by its specific inhibitor PHPS1 or by siRNA-mediated depletion was found to reduce the production of IL-25 in epithelial cells as well as the up-regulated LPS-triggered activation of JNK but not p38. To confirm the role of intra-bronchial epithelial Shp2 in OVA-induced allergic reaction, we generated CC10-rtTA/(tetO)7-Cre/Shp2^f/f mice, where Shp2 was conditionally knocked out in bronchial epithelial cells. Surprisingly, specific deletion of Shp2 in bronchial epithelial cells showed a mild but insignificant effect on the expressions of epithelium-derived cytokines as well as TH2 and TH17 polarization following allergen-induced murine airway inflammation. Collectively, our data suggested that deletion of Shp2 impaired IL-25 production in bronchial epithelial cells in vitro, but might yet have minor influence on OVA-induced allergic reaction in vivo.

Recent advances on CD4+ T cells in atherosclerosis and its implications for therapy

Atherosclerosis is an arterial inflammatory disease and the primary cause of cardiovascular disease. T helper (Th) cells are an important part in atherosclerotic plaque as they can be either disease promoting or protective. A body of evidence points to a pro-atherosclerotic role of Th1 cells, whereas the role of Th2, Th17 and iNKT cells seems more complex and dependent on surrounding factors, including the developmental stage of the disease. Opposed to Th1 cells, there is convincing support for an anti-atherogenic role of Tregs. Recent data identify the plasticity of Th cells as an important challenge in understanding the functional role of different Th cell subsets in atherosclerosis. Much of the knowledge of Th cell function in atherosclerosis is based on findings from experimental models and translating this into human disease is challenging. Targeting Th cells and/or their specific cytokines represents an attractive option for future therapy against atherosclerosis, although the benefits and the risk of modulation of Th cells with these novel drug targets must first be carefully assessed.

Update on interleukin-17: a role in the pathogenesis of inflammatory arthritis and implication for clinical practice

Interleukin-17 (IL-17A) is a cytokine critical for the acute defence against extracellular bacterial and fungal infections. Excess production during chronic inflammation has been associated with many inflammatory and autoimmune disorders. The present review describes the key molecules of the IL-17 pathway, which are or could be targeted for treatment. Since targeting of IL-17A may affect defence mechanisms, the pathogenesis of such possible adverse events is analysed. Then the contributions of IL-17 to bone changes in various forms of arthritis are discussed. Finally, the results of current inhibitors of the IL-17 pathway in clinical trials are detailed. IL-17A inhibition has been first registered for the treatment of psoriasis, psoriatic arthritis and ankylosing spondylitis. Other therapeutic options are now tested in a long list of diseases.

Neuroimmune Modulation of Gut Function

Neuroimmune communications are facilitated by the production of neurotransmitters by immune cells and the generation of immune mediators by immune cells, which form a functional entity called the "neuroimmune synapse." There are several mechanisms that further facilitate neuroimmune interactions including the anatomic proximity between immune cells and nerves, the expression of receptors for neurotransmitters on immune cells and for immune mediators on nerves, and the receptor-mediated activation of intracellular signaling pathways that modulate nerve and immune phenotype and function. The bidirectional communication between nerves and immune cells is implicated in allostasis, a process that describes the continuous adaptation to an ever-changing environment. Neuroimmune interactions are amplified during inflammation by the influx of activated immune cells that significantly alter the microenvironment. In this context, the types of neurotransmitters released by activated neurons or immune cells can exert pro- or anti-inflammatory effects. Dysregulation of the enteric nervous system control of gastrointestinal functions, such as epithelial permeability and secretion as well as smooth muscle contractility, also contribute to the chronicity of inflammation. Persistent active inflammation in the gut leads to neuroimmune plasticity, which is a structural and functional remodeling in both the neural and immune systems. The importance of neuroimmune interactions has made them an emerging target in the development of novel therapies for GI pathologies.

IL-25 attenuates rheumatoid arthritis through suppression of Th17 immune responses in an IL-13-dependent manner

IL-25, a new member of the IL-17 cytokine family, is involved in type 2 immunity initiation and has been associated with the pathogenesis of rheumatoid arthritis (RA). However, its exact role remains unclear. Here, we aimed to analyse IL-25 expression in the serum and synovial fluid of RA patients and evaluated the correlations between serum IL-25 levels, clinical and laboratory values and inflammation cytokines. Additionally, we investigated whether IL-25 can suppress Th1/Th17 responses involved in RA pathogenesis. We further determined whether IL-25 can alleviate collagen-induced arthritis (CIA) development in mice and the underlying mechanisms using in vitro and in vivo experiments. Our results showed that IL-25 was upregulated in the serum and synovial fluid of RA patients. Increased serum IL-25 levels were associated with disease severity and inflammatory response in RA patients. Furthermore, IL-25 inhibited CD4⁺ T-cell activation and differentiation into Th17 cells, without affecting Th1 cells in human RA and CIA models. Administration of IL-25 could attenuate CIA development by Th17 suppression in an IL-13-dependent manner. Our findings indicate that IL-25 plays a potent immunosuppressive role in the pathogenesis of RA and CIA by downregulating Th17 cell response, and thus, may be a potential therapeutic agent for RA.

The epithelial barrier and immunoglobulin A system in allergy

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

The microbiota and immune response during Clostridium difficile infection

Clostridium difficile is a gram-positive, spore forming anaerobe that infects the gut when the normal microbiota has been disrupted. C. difficile infection (CDI) is the most common cause of hospital acquired infection in the United States, and the leading cause of death due to gastroenteritis. Patients suffering from CDI have varying symptoms which range from mild diarrhea to pseudomembranous colitis and death. The involvement of the immune response to influence disease severity is just beginning to be investigated. There is evidence that the immune response can facilitate either protective or pathogenic phenotypes, suggesting it plays a multifaceted role during CDI. In addition to the immune response, the microbiota is pivotal in dictating the pathogenesis to CDI. A healthy microbiota effectively inhibits infection by restricting the ability of C. difficile to expand in the colon. Thus, understanding which immune mediators and components of the microbiota play beneficial roles during CDI will be important to future therapeutic developments. This review outlines how the microbiota can modulate specific immune mediators, such as IL-23 and others, to influence disease outcome.

Pro- and anti-inflammatory cytokines in cutaneous leishmaniasis: a review

Cutaneous leishmaniasis (CL) is caused by different species of the genus Leishmania. Pro- and anti-inflammatory cytokines play different roles in resistance/susceptibility and the immunopathogenesis of Leishmania infection. The balance and dynamic changes in cytokines may control or predict clinical outcome. T helper 1 (Th1) inflammatory cytokines (especially interferon-γ, tumor necrosis factor-α and interleukin-12) are the crucial factors in the initiation of protective immunity against L. major infection, whereas T helper 2 cytokines including IL-5, IL-4, and IL-13 facilitate the persistence of parasites by downregulating the Th1 immune response. On the other hand, aggravation of inflammatory reactions leads to collateral tissue damage and formation of ulcer. For this reason, immunity system such as T regulatory cells produce regulatory cytokines such as transforming growth factor-β and IL-10 to inhibit possible injures caused by increased inflammatory responses in infection site. In this article, we review the role of pro- and anti-inflammatory cytokines in the immunoprotection and immunopathology of CL.

Risk of self-harm and nonfatal suicide attempts, and completed suicide in patients with psoriasis: a population-based cohort study

BACKGROUND

Psoriasis is a common inflammatory skin disease, and inflammation may affect suicidal behaviour. Current data on the incidence and risk of suicidal behaviour in patients with psoriasis are scarce.

OBJECTIVES

We investigated the association between psoriasis and the risk of self-harm and suicide attempts and suicides.

METHODS

All Danish patients aged ≥ 18 years with mild or severe psoriasis (cases) from 1 January 1997 to 31 December 2011 were matched on age, sex and calendar time 1 : 5 with healthy controls. The outcome was a diagnosis of self-harm or a nonfatal suicide attempt, or completed suicide. Incidence rates per 10 000 person-years were calculated, and incidence rate ratios (IRRs) and confidence intervals (CIs) were estimated by Poisson regression models.

RESULTS

The study cohort comprised 408 663 individuals, including 57 502 and 11 009 patients with mild and severe psoriasis, respectively. In total 280 cases of self-harm or suicide attempts, and 574 suicides occurred during follow-up. There was no increased risk of self-harm or suicide attempts in patients with mild psoriasis (IRR 1·01, 95% CI 0·17-2·01), but this risk was significantly increased in severe psoriasis (IRR 1·69, 95% CI 1·00-2·84). There was no increased risk of suicides in mild (IRR 1·05, 95% CI 0·84-1·32) or severe psoriasis (IRR 0·78, 95% CI 0·45-1·36). Similar results were found when suicides were confirmed by official forensic investigations, and when psoriasis was compared with atopic dermatitis.

CONCLUSIONS

We found limited evidence to suggest an increased risk of self-harm and nonfatal suicide attempts in patients with psoriasis. Importantly, after adjustment for psoriatic arthritis this risk was no longer significantly increased. The risk of completed suicide was also not increased, regardless of psoriasis severity.

Microbiota-Regulated IL-25 Increases Eosinophil Number to Provide Protection during Clostridium difficile Infection

Clostridium difficile infection (CDI) is the most common cause of hospital-acquired infection in the United States. Host susceptibility and the severity of infection are influenced by disruption of the microbiota and the immune response. However, how the microbiota regulate immune responses to mediate CDI outcome remains unclear. Here, we have investigated the role of the microbiota-linked cytokine IL-25 during infection. Intestinal IL-25 was suppressed during CDI in humans and mice. Restoration of IL-25 reduced CDI-associated mortality and tissue pathology even though equivalent levels of C. difficile bacteria and toxin remained in the gut. IL-25 protection was mediated by gut eosinophils, as demonstrated by an increase in intestinal eosinophils and a loss of IL-25 protection upon eosinophil depletion. These findings support a mechanism whereby the induction of IL-25-mediated eosinophilia can reduce host mortality during active CDI. This work may provide targets for future development of microbial or immune-based therapies.

Helicobacter hepaticus and bowel disease progression

There are six main kinds of Helicobacter (H.) associated with human infection, namely, H. pylori, H. bizzozeronii, H. cinaedi, H. canis, H. canadensis, and H. feils. In recent years, there have been a number of research and clinical reports of H. hepaticus and H. Bilis. In this paper, we review the bacteriology of Helicobacter hepaticus and its association with the pathogenesis of enteropathy.

Acute blockade of IL-25 in a colitis associated colon cancer model leads to increased tumor burden

Chronic inflammation within the gastrointestinal tract results in an increased risk for developing colorectal cancer. Epithelial cytokines, including interleukin-25 (IL-25), are produced in the colon and are critical for protection from parasites, but can also be pathogenic in the context of inflammatory bowel diseases and allergy. Whether IL-25 is involved in the progression from inflammation to cancer is still largely unexplored. Using a well-established murine model for colitis-induced colon cancer; we aimed to determine the role of IL-25 in this process. We found that acute IL-25 blockade resulted in greater tumor burdens compared to isotype control treated mice. Histologically, α-IL-25 treated mice had increased colitis scores compared to mice receiving isotype control antibody, as well as decreased eosinophilia. This is the first study to explore the therapeutic potential of using an IL-25 blocking antibody during a chronic inflammatory setting. Taken together these data suggest that IL-25 plays an inhibitory role in the growth and development of colonic tumors.

Interleukin-25 is detrimental for recovery after spinal cord injury in mice

Background

The cytokine, interleukin (IL)-25, is thought to be critically involved in inducing a type 2 immune response which may contribute to regeneration after central nervous system (CNS) trauma. We investigated whether applying recombinant IL-25, locally or systemically, in a mouse model of spinal cord injury (SCI) improves functional and histological recovery.

Findings

Repeated systemic administration of IL-25 did not influence functional recovery following SCI. In contrast, a single local administration of IL-25 significantly worsened locomotor outcome, which was evident from a decreased Basso mouse scale (BMS) score compared with phosphate-buffered saline (PBS)-treated controls. This was accompanied by a significant increase in lesion size, demyelination, and T helper cell infiltration.

Conclusions

These data show for the first time that IL-25 is either ineffective when applied systemically or detrimental to spinal cord recovery when applied locally. Our findings question the potential neuroprotective role of IL-25 following CNS trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0566-y) contains supplementary material, which is available to authorized users.