Deletion of IL-33R (ST2) abrogates resistance to EAE in BALB/C mice by enhancing polarization of APC to inflammatory phenotype

Targeted proteomics of cerebrospinal fluid in treatment naïve multiple sclerosis patients identifies immune biomarkers of clinical phenotypes

Multiple sclerosis (MS) is an inflammatory demyelinating disease with heterogeneous clinical presentations and variable long-term disability accumulation. There are currently no standard criteria to accurately predict disease outcomes. In this study we investigated the cross-sectional relationship between disease phenotype and immune-modulating cytokines and chemokines in cerebrospinal fluid (CSF). We analyzed CSF from 20 DMT-naïve MS patients using Olink Proteomics' Target 96 Inflammation panel and correlated the resulting analytes with respect to (1) disease subtype, (2) patient age and sex, (3) extent of clinical disability, and (4) MRI segmental brain volumes. We found that intrathecal IL-4 correlated with higher Expanded Disability Status Scale (EDSS) scores and longer 25-foot walk times, and CD8A correlated with decreased thalamic volumes and longer 9-hole peg test times. Male sex was associated with higher FGF-19 expression, and Tumefactive MS with elevated CCL4. Several inflammatory markers were correlated with older age at the time of LP. Finally, higher intrathecal IL-33 correlated with increased MS lesion burden and multi-compartment brain atrophy. This study confirms immune heterogeneity underlying CSF profiles in MS, but also identifies several inflammatory protein biomarkers that may be of use for predicting clinical outcomes in future algorithms.

Adipose-derived mesenchymal stem cells ameliorates experimental autoimmune encephalomyelitis via modulation of Th1/Th17 and expansion of Th2/Treg responses

The most common central nervous system (CNS) inflammatory disease is multiple sclerosis (MS), modeled using experimental autoimmune encephalomyelitis (EAE). Mesenchymal stem cells (MSCs) exhibit potent immunomodulatory capabilities, including the suppression of immune cell functions and anti-inflammatory cytokine production. Female C57BL/6 mice (8-10 weeks old) were divided into three groups: 1. Control, 2. Allogeneic MSCs (ALO) treatment, and 3. Syngeneic MSCs (SYN) treatment. To induce EAE, myelin oligodendrocyte glycoprotein was injected subcutaneously with complete Freund's adjuvant, followed by intraperitoneal pertussis toxin. On Days 6 and 12 postimmunization, the treatment groups received intraperitoneal injections of 2 × 106 MSCs. Daily clinical and weight assessments were performed, and on Day 25, the mice were euthanized. At the end of the period, brain histological analysis was conducted to quantify lymphocyte infiltration. T-cell characteristics were determined using enzyme-linked immunosorbent assay and Real-time polymerase chain reaction (RT-PCR). The assessment of transcription factor expression levels in the CNS was also performed using RT-PCR. Compared to the control group, both the allogeneic (ALO) and syngeneic (SYN) groups demonstrated significantly reduced disease progression. The maximum clinical scores for the control, ALO, and SYN groups were 4.4 ± 0.1, 2.4 ± 0.2, and 2.1 ± 0.2, respectively (ALO and SYN vs. Control: p < .001). In comparison to the control group, histological studies demonstrated that the allogeneic and syngeneic groups had less lymphocytic infiltration (ALO: 1.4 ± 0.1, SYN: 1.2 ± 0.2, and control: 2.8 ± 0.15; p < .001) and demyelination (ALO: 1.2 ± 0.15, SYN: 1.1 ± 0.1 and control: 2.9 ± 0.1, p < .001). ALO and SYN groups had lower expression of Th1 and Th17 cytokines and transcription factors (IFN-γ: 0.067, 0.051; STAT4: 0.189, 0.162; T-bet: 0.175, 0.163; IL-17: 0.074, 0.061; STAT3: 0.271, 0.253; ROR-γt: 0.163, 0.149, respectively) compared to the control group on Day 25 following EAE induction. Additionally, ALO and SYN groups compared to the control group, expressed more Th2 and Treg cytokines and transcription factors (IL-4: 4.25, 4.63; STAT6: 2.78, 2.96; GATA3: 2.91, 3.08; IL-27: 2.32, 2.46, IL-33: 2.71, 2.85; TGF-β: 4.8, 5.05; IL-10: 4.71, 4.93; CTLA-4: 7.72, 7.95; PD1: 4.12,4.35; Foxp3: 3.82,4.08, respectively). This research demonstrated that MSCs possess the potential to be a therapeutic option for MS and related CNS inflammatory disorders. Their immunomodulatory properties, coupled with the observed reductions in disease severity, lymphocytic infiltration, and demyelination, indicate that MSCs could play a crucial role in altering the course of MS by mitigating inflammatory immune responses and promoting regulatory immune processes. These findings open up new possibilities for the development of MSC-based therapies for MS, and further investigation and clinical trials may be warranted to explore their efficacy and safety in human patients.

IL-33/ST2 axis in autoimmune disease

Interleukin-33 (IL-33) is a member of the IL-1 family and plays an ambivalent role in autoimmune diseases. IL-33 signals via the ST2 receptor and drives cytokine production in mast cells, basophils, eosinophils, NK cells, and T lymphocyte cells. The vital role of IL-33 as an active component gives rise to aberrant local and systemic damage which has been demonstrated in numerous inflammatory disorders and immune-mediated pathological conditions including multiple sclerosis (MS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis, Sjogren's syndrome, inflammatory bowel disease (IBD), etc. IL-33/ST2 axis can up-regulate pro-inflammatory cytokine release in autoimmune disease, however, in some metabolic diseases like diabetes mellitus type 1 IL-33 can be considered an anti-inflammatory cytokine. The purpose of this review is to discuss selected studies on IL-33/ST2 axis in autoimmune diseases and its potential role as a pathogenic or protective cytokine.

Dual roles of interleukin-33 in cognitive function by regulating central nervous system inflammation

With the advent of an aging society, the incidence of dementia is increasing, resulting in a vast burden on society. It is increasingly acknowledged that neuroinflammation is implicated in various neurological diseases with cognitive dysfunction such as Alzheimer’s disease, multiple sclerosis, ischemic stroke, traumatic brain injury, and central nervous system infections. As an important neuroinflammatory factor, interleukin-33 (IL-33) is highly expressed in various tissues and cells in the mammalian brain, where it plays a role in the pathogenesis of a number of central nervous system conditions. Reams of previous studies have shown that IL-33 has both pro- and anti-inflammatory effects, playing dual roles in the progression of diseases linked to cognitive impairment by regulating the activation and polarization of immune cells, apoptosis, and synaptic plasticity. This article will summarize the current findings on the effects IL-33 exerts on cognitive function by regulating neuroinflammation, and attempt to explore possible therapeutic strategies for cognitive disorders based on the adverse and protective mechanisms of IL-33.

Targeting the Epithelium-Derived Innate Cytokines: From Bench to Bedside

When epithelial cells are exposed to potentially threatening external stimuli such as allergens, bacteria, viruses, and helminths, they instantly produce "alarmin" cytokines, namely, IL-33, IL-25, and TSLP. These alarmins alert the immune system about these threats, thereby mobilizing host immune defense mechanisms. Specifically, the alarmins strongly stimulate type-2 immune cells, including eosinophils, mast cells, dendritic cells, type-2 helper T cells, and type-2 innate lymphoid cells. Given that the alarm-raising role of IL-33, IL-25, and TSLP was first detected in allergic and infectious diseases, most studies on alarmins focus on their role in these diseases. However, recent studies suggest that alarmins also have a broad range of effector functions in other pathological conditions, including psoriasis, multiple sclerosis, and cancer. Therefore, this review provides an update on the epithelium-derived cytokines in both allergic and non-allergic diseases. We also review the progress of clinical trials on biological agents that target the alarmins and discuss the therapeutic potential of these agents in non-allergic diseases.

The NF-κB Transcription Factor c-Rel Modulates Group 2 Innate Lymphoid Cell Effector Functions and Drives Allergic Airway Inflammation

Group 2 innate lymphoid cells (ILC2s) play a key role in the initiation and orchestration of early type 2 immune responses. Upon tissue damage, ILC2s are activated by alarmins such as IL-33 and rapidly secrete large amounts of type 2 signature cytokines. ILC2 activation is governed by a network of transcriptional regulators including nuclear factor (NF)-κB family transcription factors. While it is known that activating IL-33 receptor signaling results in downstream NF-κB activation, the underlying molecular mechanisms remain elusive. Here, we found that the NF-κB subunit c-Rel is required to mount effective innate pulmonary type 2 immune responses. IL-33-mediated activation of ILC2s in vitro as well as in vivo was found to induce c-Rel mRNA and protein expression. In addition, we demonstrate that IL-33-mediated activation of ILC2s leads to nuclear translocation of c-Rel in pulmonary ILC2s. Although c-Rel was found to be a critical mediator of innate pulmonary type 2 immune responses, ILC2-intrinsic deficiency of c-Rel did not have an impact on the developmental capacity of ILC2s nor affected homeostatic numbers of lung-resident ILC2s at steady state. Moreover, we demonstrate that ILC2-intrinsic deficiency of c-Rel alters the capacity of ILC2s to upregulate the expression of ICOSL and OX40L, key stimulatory receptors, and the expression of type 2 signature cytokines IL-5, IL-9, IL-13, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Collectively, our data using Rel^−/− mice suggest that c-Rel promotes acute ILC2-driven allergic airway inflammation and suggest that c-Rel may contribute to the pathophysiology of ILC2-mediated allergic airway disease. It thereby represents a promising target for the treatment of allergic asthma, and evaluating the effect of established c-Rel inhibitors in this context would be of great clinical interest.

T reg cell-intrinsic requirements for ST2 signaling in health and neuroinflammation

ST2, the receptor for the alarmin IL-33, is expressed by a subset of regulatory T (T reg) cells residing in nonlymphoid tissues, and these cells can potently expand upon provision of exogenous IL-33. Whether the accumulation and residence of T reg cells in tissues requires their cell-intrinsic expression of and signaling by ST2, or whether indirect IL-33 signaling acting on other cells suffices, has been a matter of contention. Here, we report that ST2 expression on T reg cells is largely dispensable for their accumulation and residence in nonlymphoid organs, including the visceral adipose tissue (VAT), even though cell-intrinsic sensing of IL-33 promotes type 2 cytokine production by VAT-residing T reg cells. In addition, we uncovered a novel ST2-dependent role for T reg cells in limiting the size of IL-17A–producing γδT cells in the CNS in a mouse model of neuroinflammation, experimental autoimmune encephalomyelitis (EAE). Finally, ST2 deficiency limited to T reg cells led to disease exacerbation in EAE.

Functional immune cell-astrocyte interactions

Astrocytes are abundant glial cells in the central nervous system (CNS) that control multiple aspects of health and disease. Through their interactions with components of the blood–brain barrier (BBB), astrocytes not only regulate BBB function, they also sense molecules produced by peripheral immune cells, including cytokines. Here, we review the interactions between immune cells and astrocytes and their roles in health and neurological diseases, with a special focus on multiple sclerosis (MS). We highlight known pathways that participate in astrocyte crosstalk with microglia, NK cells, T cells, and other cell types; their contribution to the pathogenesis of neurological diseases; and their potential value as therapeutic targets.

Therapeutic Opportunities of Interleukin-33 in the Central Nervous System

Interleukin-33 (IL-33), a member of the IL-1 cytokine family, is involved in various diseases. IL-33 exerts its effects via its heterodimeric receptor complex, which comprises suppression of tumorigenicity 2 (ST2) and the IL-1 receptor accessory protein (IL-1RAP). Increasing evidence has demonstrated that IL-33/ST2 signaling plays diverse but crucial roles in the homeostasis of the central nervous system (CNS) and the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infection, trauma, and ischemic stroke. In the current review, we focus on the functional roles and cellular signaling mechanisms of IL-33 in the CNS and evaluate the potential for diagnostic and therapeutic applications.

IL-33 promotes innate lymphoid cell-dependent IFN-γ production required for innate immunity to Toxoplasma gondii

IL-33 is an alarmin required for resistance to the parasite Toxoplasma gondii, but its role in innate resistance to this organism is unclear. Infection with T. gondii promotes increased stromal cell expression of IL-33, and levels of parasite replication correlate with release of IL-33 in affected tissues. In response to infection, a subset of innate lymphoid cells (ILC) emerges composed of IL-33R+ NK cells and ILC1s. In Rag1-/-mice, where NK cells and ILC1 production of IFN-γ mediate innate resistance to T. gondii, the loss of the IL-33R resulted in reduced ILC responses and increased parasite replication. Furthermore, administration of IL-33 to Rag1-/- mice resulted in a marked decrease in parasite burden, increased production of IFN-γ, and the recruitment and expansion of inflammatory monocytes associated with parasite control. These protective effects of exogenous IL-33 were dependent on endogenous IL-12p40 and the ability of IL-33 to enhance ILC production of IFN-γ. These results highlight that IL-33 synergizes with IL-12 to promote ILC-mediated resistance to T. gondii.

ILC in chronic inflammation, cancer and targeting with biologicals

Since their discovery, Innate Lymphoid Cells (ILC) have emerged as important effector cells, serving multiple roles in maintaining tissue homeostasis and responding to tissue insults. As such, dysregulations of their function and distribution have been observed in a variety of immune-mediated diseases, suggesting a specific role for ILC in the pathophysiology of several disorders including chronic inflammation and cancer. Here, we provide an updated view on ILC biology dissecting their pathological or protective contribution in chronic inflammatory diseases such as multiple sclerosis, inflammatory bowel diseases, psoriasis, rheumatoid arthritis, asthma and COPD, atherosclerosis, also exploring ILC role in tumor surveillance and progression. Throughout the review, we will also highlight how the potential dual role of these cells for protective or pathogenic immunity in many inflammatory diseases makes them interesting targets for the development of novel therapeutic strategies, particularly promising.

The Role of the IL-33/ST2 Immune Pathway in Autoimmunity: New Insights and Perspectives

Interleukin (IL)-33, a member of IL-1 cytokine family, is produced by various immune cells and acts as an alarm to alert the immune system after epithelial or endothelial cell damage during cell necrosis, infection, stress, and trauma. The biological functions of IL-33 largely depend on its ligation to the corresponding receptor, suppression of tumorigenicity 2 (ST2). The pathogenic roles of this cytokine have been implicated in several disorders, including allergic disease, cardiovascular disease, autoimmune disease, infectious disease, and cancers. However, alerted levels of IL-33 may result in either disease amelioration or progression. Genetic variations of IL33 gene may confer protective or susceptibility risk in the onset of autoimmune diseases. The purpose of this review is to discuss the involvement of IL-33 and ST2 in the pathogenesis of a variety of autoimmune disorders, such as autoimmune rheumatic, neurodegenerative, and endocrine diseases.

Type 17 Immune Response Facilitates Progression of Inflammation and Correlates with Cognition in Stable Schizophrenia

Dysregulation of the type 17 immune pathway has already been considered in schizophrenia and we previously measured decreased sera values of interleukin (IL)-17 in early stages. We further explored the possible correlation of IL-17 systemic levels with proinflammatory cytokines and cognitive scores and additionally analyzed the percentage of IL-17 producing lymphocytes in peripheral blood of patients with stable schizophrenia. We included 27 patients diagnosed with schizophrenia (F20), after a three-month stable depot antipsychotic therapy (risperidone or paliperidone) and 18 healthy control subjects. Positive and Negative Syndrome Scale of Schizophrenia and the Montreal-Cognitive Assessment (MoCA) were conducted. Sera concentrations of IL-17, IL-6, tumor necrosis factor alpha (TNF-α) and soluble ST2 receptor (sST2) were measured. Flow cytometry and Natural Killer (NK) and T cell analyses were done in 10 patients and 10 healthy controls. Moderate positive correlation was established between IL-17 and TNF-α (r = 0.640; p = 0.001), IL-17 and IL-6 (r = 0.514; p = 0.006), IL-17 and sST2 (r = 0.394; p = 0.042). Furthermore, a positive correlation between the serum levels of IL-17 and MoCA scores was observed, especially with visuospatial and executive functioning, as well as language functioning and delayed recall (p < 0.05). Significantly higher percentage of IL-17 producing CD56⁺ NK cells was measured in peripheral blood of patients with schizophrenia in remission vs. healthy individuals (p = 0.001). The percentage of CD4⁺ T cells and CD4⁺ T cells that produce IL-17 was significantly increased in patients (p = 0.001). This study revealed the involvement of innate type 17 immune response in the progression of inflammation and this could be related to cognitive functioning in stable schizophrenia.

The Helminth Parasite Heligmosomoides polygyrus Attenuates EAE in an IL-4Rα-Dependent Manner

Helminth parasites are effective in biasing Th2 immunity and inducing regulatory pathways that minimize excessive inflammation within their hosts, thus allowing chronic infection to occur whilst also suppressing bystander atopic or autoimmune diseases. Multiple sclerosis (MS) is a severe autoimmune disease characterized by inflammatory lesions within the central nervous system; there are very limited therapeutic options for the progressive forms of the disease and none are curative. Here, we used the experimental autoimmune encephalomyelitis (EAE) model to examine if the intestinal helminth Heligmosomoides polygyrus and its excretory/secretory products (HES) are able to suppress inflammatory disease. Mice infected with H. polygyrus at the time of immunization with the peptide used to induce EAE (myelin-oligodendrocyte glycoprotein, pMOG), showed a delay in the onset and peak severity of EAE disease, however, treatment with HES only showed a marginal delay in disease onset. Mice that received H. polygyrus 4 weeks prior to EAE induction were also not significantly protected. H. polygyrus secretes a known TGF-β mimic (Hp-TGM) and simultaneous H. polygyrus infection with pMOG immunization led to a significant expansion of Tregs; however, administering the recombinant Hp-TGM to EAE mice failed to replicate the EAE protection seen during infection, indicating that this may not be central to the disease protecting mechanism. Mice infected with H. polygyrus also showed a systemic Th2 biasing, and restimulating splenocytes with pMOG showed release of pMOG-specific IL-4 as well as suppression of inflammatory IL-17A. Notably, a Th2-skewed response was found only in mice infected with H. polygyrus at the time of EAE induction and not those with a chronic infection. Furthermore, H. polygyrus failed to protect against disease in IL-4Rα^−/− mice. Together these results indicate that the EAE disease protective mechanism of H. polygyrus is likely to be predominantly Th2 deviation, and further highlights Th2-biasing as a future therapeutic strategy for MS.

IL-33 and its decoy sST2 in patients with Alzheimer's disease and mild cognitive impairment

BACKGROUND

Interleukin-33 is a cytokine endowed with pro- and anti-inflammatory properties that plays a still poorly defined role in the pathogenesis of a number of central nervous system (CNS) conditions including Alzheimer's disease (AD). We analyzed this cytokine and its decoy receptor sST2 in Alzheimer's disease (AD) and mild cognitive impairment (MCI).

METHOD

IL-33 and sST2 were analyzed in serum and CSF of AD and MCI patients, comparing the results to those obtained in age-matched healthy controls (HC). Because of the ambiguous role of IL-33 in inflammation, the concentration of both inflammatory (IL-1β and IL-6) and anti-inflammatory (IL-10) cytokines was analyzed as well in serum and cerebrospinal fluid (CSF) of the same individuals. Finally, the effect of IL-33 on in vitro Aβ₄₂-stimulated monocytes of AD, MCI, and HC individuals was examined.

RESULTS

As compared to HC, (1) IL-33 was significantly decreased in serum and CSF of AD and MCI, (2) sST2 was increased in serum of AD and MCI but was undetectable in CSF, (3) serum and CSF IL-1β concentration was significantly increased and that of IL-10 was reduced in AD and MCI, whereas no differences were observed in IL-6. In vitro addition of IL-33 to LPS+Aβ ₄₂-stimulated monocytes downregulated IL-1β generation in MCI and HC, but not in AD, and stimulated IL-10 production in HC alone. IL-33 addition also resulted in a significant reduction of NF-kB nuclear translocation in LPS+Aβ₄₂-stimulated monocytes of HC alone.

CONCLUSIONS

These data support the hypothesis that IL-33 plays a complex anti-inflammatory role that is lost in AD- and MCI-associated neuroinflammation; results herein also suggest a possible use of IL-33 as a novel therapeutic approach in AD and MCI.

Interleukin-17 in Chronic Inflammatory Neurological Diseases

A critical role for IL-17, a cytokine produced by T helper 17 (Th17) cells, has been indicated in the pathogenesis of chronic inflammatory and autoimmune diseases. A positive effect of blockade of IL-17 secreted by autoreactive T cells has been shown in various inflammatory diseases. Several cytokines, whose production is affected by environmental factors, control Th17 differentiation and its maintenance in tissues during chronic inflammation. The roles of IL-17 in the pathogenesis of chronic neuroinflammatory conditions, multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), Alzheimer's disease, and ischemic brain injury are reviewed here. The role of environmental stimuli in Th17 differentiation is also summarized, highlighting the role of viral infection in the regulation of pathogenic T helper cells in EAE.

Dual immune functions of IL-33 in inflammatory bowel disease

Interleukin-33 (IL-33) has emerged as a critical regulator in a variety of diseases, including inflammatory bowel disease (IBD). IL-33 can be produced by various tissues and cells, and typically induces Th2-type immune responses via binding to the receptor ST2. In addition, accumulated data have shown that IL-33 also plays a modulatory role in the function of regulatory T cells (Tregs), B cells, and innate immune cells such as macrophages and innate lymphoid cells (ILCs). IBD, including Crohn's disease and ulcerative colitis, are characterized by aberrant immunological responses leading to intestinal tissue injury and destruction. Although IL-33 expression is increased in IBD patients and correlates with the patients' disease activity index, mechanistic studies to date have demonstrated both pathogenic and protective roles in animal models of experimental colitis. In this review, we will summarize the roles and mechanisms of IL-33 in IBD, which is essential to understand the pathogenesis of IBD and determine potential therapies.

IL-33/IL-33R in various types of carotid artery atherosclerotic lesions

OBJECTIVE

Inflammation plays a crucial role in the progression of atherosclerotic plaques. The aim of the study was to investigate serum levels and expression of Interleukin-33 (IL-33) and ST2 receptor in atherosclerotic plaques and to analyze correlation with the type of the carotid plaques in patients with carotid disease.

METHODS

This study included 191 consecutive patients submitted for carotid endarterectomy (CEA). Preoperative serum levels of IL-33 and soluble ST2 (sST2) were measured. Atherosclerotic plaques obtained during surgery were initially histologically classified and immunohistochemical analyzes of IL-33, IL-33R, CD68 and alpha-SMA expression was performed. Ultrasound assessment of the level of carotid stenosis in each patient was performed prior to carotid surgery. Demographic and clinical data such as gender, age, smoking status, blood pressure, glycaemia, hemoglobin and creatinine levels, and comorbidities were collected and the comparisons between variables were statistically evaluated.

RESULTS

Serum levels of IL-33 (35.86 ± 7.93 pg/ml vs.12.29 ± 1.8 pg/ml, p < 0.05) and sST2 (183 ± 8.03 pg/ml vs. 122.31 ± 15.89 pg/ml, p < 0.05) were significantly higher in the group of CEA patients vs. healthy subjects. We demonstrated abundant tissue expression of IL-33 and ST2 in atherosclerotic carotid artery lesions. The levels of IL-33 and IL-33R expression were significantly higher in vulnerable plaques and significantly correlated with the degree of inflammatory cells infiltration in these plaques (R = 0.579, p = 0.049). Immunohistochemical analysis also revealed that cells responsible for IL-33 expression are not only mononuclear cells confined to inflammatory atherosclerotic lesions, but also smooth muscle cells which gained phenotypic characteristics of foam cells and were loaded with lipid droplets.

CONCLUSION

The obtained results confirm the importance of IL-33/ST2 axis in the process of atherosclerosis, and indicate its ambiguous function in immune response, whether as proinflammatory cytokine in advanced atherosclerotic lesions, or as profibrotic, in early lesions.

Pleiotropic Effects of IL-33 on CD4+ T Cell Differentiation and Effector Functions

IL-33, a member of the IL-1 family of cytokines, was originally described in 2005 as a promoter of type 2 immune responses. However, recent evidence reveals a more complex picture. This cytokine is released locally as an alarmin upon cellular damage where innate cell types respond to IL-33 by modulating their differentiation and influencing the polarizing signals they provide to T cells at the time of antigen presentation. Moreover, the prominent expression of the IL-33 receptor, ST2, on GATA3+ T helper 2 cells (TH2) demonstrated that IL-33 could have a direct impact on T cells. Recent observations reveal that T-bet+ TH1 cells and Foxp3+ regulatory T (TREG) cells can also express the ST2 receptor, either transiently or permanently. As such, IL-33 can have a direct effect on the dynamics of T cell populations. As IL-33 release was shown to play both an inflammatory and a suppressive role, understanding the complex effect of this cytokine on T cell homeostasis is paramount. In this review, we will focus on the factors that modulate ST2 expression on T cells, the effect of IL-33 on helper T cell responses and the role of IL-33 on TREG cell function.

Galectin-3 Deficiency Facilitates TNF-α-Dependent Hepatocyte Death and Liver Inflammation in MCMV Infection

Galectin-3 (Gal-3) has a role in multiple inflammatory pathways. Various, opposite roles of Gal-3 in liver diseases have been described but there are no data about the role of Gal-3 in development of hepatitis induced with cytomegalovirus infection. In this study we aimed to clarify the role of Gal-3 in murine cytomegalovirus (MCMV)-induced hepatitis by using Gal-3-deficient (Gal-3 KO) mice. Here we provide the evidence that Gal-3 has the protective role in MCMV-induced hepatitis. Enhanced hepatitis manifested by more inflammatory and necrotic foci and serum level of ALT, enhanced apoptosis and necroptosis of hepatocytes and enhanced viral replication were detected in MCMV-infected Gal-3 deficient mice. NK cells does not contribute to more severe liver damage in MCMV-infected Gal-3 KO mice. Enhanced expression of TNF-α in the hepatocytes of Gal-3 KO mice after MCMV infection, abrogated hepatocyte death, and attenuated inflammation in the livers of Gal-3 KO mice after TNF-α blockade suggest that TNF-α plays the role in enhanced disease in Gal-3 deficient animals. Treatment with recombinant Gal-3 reduces inflammation and especially necrosis of hepatocytes in the livers of MCMV-infected Gal-3 KO mice. Our data highlight the protective role of Gal-3 in MCMV-induced hepatitis by attenuation of TNF-α-mediated death of hepatocytes.

Long-term interleukin-33 treatment delays disease onset and alleviates astrocytic activation in a transgenic mouse model of amyotrophic lateral sclerosis

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Th2-type cytokine IL-33 delayed the disease onset of female SOD1-G93 A transgenic ALS mice.

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IL-33 decreased the proportion of T cells in the spleens and lymph nodes of female mice.

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IL-33 decreased astrocytic activation in the spinal cord of female mice.

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Male mice were unresponsive to the treatment.

Inflammation is a prominent feature of the neuropathology of amyotrophic lateral sclerosis (ALS). Emerging evidence suggests that inflammatory cascades contributing to the disease progression are not restricted to the central nervous system (CNS) but also occur peripherally. Indeed, alterations in T cell responses and their secreted cytokines have been detected in ALS patients and in animal models of ALS. One key cytokine responsible for the shift in T cell responses is interleukin-33 (IL-33), which stimulates innate type 2 immune cells to produce a large amount of Th2 cytokines that are possibly beneficial in the recovery processes of CNS injuries. Since the levels of IL-33 have been shown to be decreased in patients affected with ALS, we sought to determine whether a long-term recombinant IL-33 treatment of a transgenic mouse model of ALS expressing G93A-superoxide dismutase 1 (SOD1-G93A) alters the disease progression and ameliorates the ALS-like disease pathology. SOD1-G93A mice were treated with intraperitoneal injections of IL-33 and effects on disease onset and inflammatory status were determined. Spinal cord (SC) neurons, astrocytes and T-cells were exposed to IL-33 to evaluate the cell specific responses to IL-33. Treatment of SOD1-G93A mice with IL-33 delayed the disease onset in female mice, decreased the proportion of CD4+ and CD8 + T cell populations in the spleen and lymph nodes, and alleviated astrocytic activation in the ventral horn of the lumbar SC. Male SOD1-G93A mice were unresponsive to the treatment. In vitro studies showed that IL-33 is most likely not acting directly on neurons and astrocytes, but rather conveying its effects through peripheral T-cells. Our results suggest that strategies directed to the peripheral immune system may have therapeutic potential in ALS. The effect of gender dimorphisms to the treatment efficacy needs to be taken into consideration when designing new therapeutic strategies for CNS diseases.

Expression and Function of IL-33/ST2 Axis in the Central Nervous System Under Normal and Diseased Conditions

Interleukin-33 (IL-33) is a well-recognized immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. The abundant expression of IL-33 in brain and spinal cord prompted many scientists to explore its unique role in the central nervous system (CNS) under physiological and pathological conditions. Indeed emerging evidence from over a decade's research suggests that IL-33 acts as one of the key molecular signaling cues coordinating the network between the immune and CNS systems, particularly during the development of neurological diseases. Here, we highlight the recent advances in our knowledge regarding the distribution and cellular localization of IL-33 and its receptor ST2 in specific CNS regions, and more importantly the key roles IL-33/ST2 signaling pathway play in CNS function under normal and diseased conditions.

IL-33 Prevents MLD-STZ Induction of Diabetes and Attenuate Insulitis in Prediabetic NOD Mice

Type 1 diabetes is an autoimmune disease caused by the immune-mediated destruction of pancreatic β-cells. Prevention of type 1 diabetes requires early intervention in the autoimmune process against beta-cells of the pancreatic islets of Langerhans, which is believed to result from disordered immunoregulation. CD4+Foxp3+ regulatory T cells (Tregs) participate as one of the most important cell types in limiting the autoimmune process. The aim of this study was to investigate the effect of exogenous IL-33 in multiple low dose streptozotocin (MLD-STZ) induced diabetes and to delineate its role in the induction of protective Tregs in an autoimmune attack. C57BL/6 mice were treated i. p. with five doses of 40 mg/kg STZ and 0.4 μg rIL-33 four times, starting from day 0, 6, or 12 every second day from the day of disease induction. 16 weeks old NOD mice were treated with 6 injections of 0.4 μg/mouse IL-33 (every second day). Glycemia and glycosuria were measured and histological parameters in pancreatic islets were evaluated at the end of experiments. Cellular make up of the pancreatic lymph nodes and islets were evaluated by flow cytometry. IL-33 given simultaneously with the application of STZ completely prevented the development of hyperglycemia, glycosuria and profoundly attenuated mononuclear cell infiltration. IL-33 treatment was accompanied by higher number of IL-13 and IL-5 producing CD4+ T cells and increased presence of ST2+Foxp3+ regulatory T cells in pancreatic lymph nodes and islets. Elimination of Tregs abrogated protective effect of IL-33. We provide evidence that exogenous IL-33 completely prevents the development of T cell mediated inflammation in pancreatic islets and consecutive development of diabetes in C57BL/6 mice by facilitating the induction Treg cells. To extend this finding for possible relevance in spontaneous diabetes, we showed that IL-33 attenuate insulitis in prediabetic NOD mice.

Interleukin-33 deficiency exacerbated experimental autoimmune encephalomyelitis with an influence on immune cells and glia cells

Interleukin (IL)-33, a member of the IL-1 cytokine family, is highly expressed in central nervous system (CNS), suggesting its potential role in CNS. Although some studies have focused on the role of IL-33 in multiple sclerosis (MS) / experimental autoimmune encephalomyelitis (EAE), an autoimmune disease characterized by demyelination and axonal damage in CNS, the exact role of IL-33 in MS/EAE remains unclear and controversial. Here, we used IL-33 knockout mice to clarify the role of endogenous IL-33 in EAE by simultaneously eliminating its role as a nuclear transcription factor and an extracellular cytokine. We found that the clinical score in IL-33 knockout EAE mice was higher accompanied by more severe demyelination compared with the wild-type (WT) EAE mice. As for the main immune cells participating in EAE in IL-33 knockout mice, pathogenic effector T cells increased both in peripheral immune organs and CNS, while CD4⁺FOXP3⁺ regulatory T cells decreased in spleen and lymph nodes, Th2 cells and natural killer (NK) cells decreased in CNS. Additionally, the populations of microglia/macrophages and CD11C⁺CD11B⁺ dendritic cells (DCs) increased in CNS of IL-33 knockout mice with EAE, among which iNOS-producing microglia/macrophages increased. Moreover, resident astrocytes/microglia were more activated in IL-33 knockout mice with EAE. In vitro, after blocking the IL-33, the proliferation of primary astrocytes, the production of MCP-1/CCL2 and TNF-α by astrocytes, and the production of TNF-α by primary microglia stimulated by the homogenate of the peak stage of EAE were increased. Our results indicate that IL-33 plays a protective role in EAE and exerts extensive influences on multiple immune cells and neural cells involved in EAE.

IL-33 receptor (ST2) deficiency downregulates myeloid precursors, inflammatory NK and dendritic cells in early phase of sepsis

BACKGROUND

Sepsis is a life-threatening disease mediated by profound disturbances in systemic inflammatory response to infection. IL-33 is multifunctional regulator of numerous aspects of innate and adaptive immune response. The aim of this article was to further evaluate the role of IL-33 receptor (ST2) in different pathways of innate immunity during early polymicrobial sepsis.

METHODS

Polymicrobial sepsis was induced using cecal ligation and puncture (CLP) model in ST2 deficient (ST2-/-) and wild type BALB/c mice. Peritoneal and spleen cells were isolated for further phenotyping. Apoptosis was determined by immunohistochemistry and flow cytometry.

RESULTS

Deletion of ST2 leads to increased susceptibility to early manifestations of sepsis as evaluated by clinical signs and survival. These are accompanied by decrease in the total number of neutrophils, eosinophils and mast cells in peritoneal cavity 12 h after CLP. In early sepsis there was also low number of precursors of myeloid cells in particular CD11b+Ly6G+Ly6Clow cells in spleen of ST2-/- mice. Although the number of NK cells in the spleen was similar, there were significant differences in the presence of inflammatory IFN-γ and IL-17 producing NK cells. Further, ST2 deletion affects the phenotype and maturation of dendritic cell in sepsis. The total number of dendritic cells in the spleen was lower as well as IL-12 expressing dendritic cells. Finally, there was higher frequency of active caspase-3 positive and early apoptotic cells, in particular CD11c positive cells, in spleen of septic ST2-/- mice.

CONCLUSION

Taken together, our data provide the evidence that ST2 deficiency in early phase of sepsis downregulates myeloid precursors, inflammatory NK and dendritic cells.

T cell-derived IFN-γ downregulates protective group 2 innate lymphoid cells in murine lupus erythematosus

Innate lymphoid cells (ILCs) are important regulators of the immune response and play a crucial role in the restoration of tissue homeostasis after injury. GATA-3⁺ IL-13- and IL-5-producing group 2 innate lymphoid cells (ILC2s) have been shown to promote tissue repair in barrier organs, but despite extensive research on ILCs in the recent years, their potential role in autoimmune diseases is still incompletely understood. In the present study, we investigate the role of ILC2s in the MRL/MpJ-Fas^lpr (MRL-lpr) mouse model for severe organ manifestation of systemic lupus erythematosus (SLE). We show that in these MRL-lpr mice, progression of lupus nephritis is accompanied with a reduction of ILC2 abundance in the inflamed renal tissue. Proliferation/survival and cytokine production of kidney-residing ILC2s was suppressed by IFN-γ and, to a lesser extent, by IL-27 which were produced by activated T cells and myeloid cells in the nephritic kidney, respectively. Most importantly, restoration of ILC2 numbers by IL-33-mediated expansion ameliorated lupus nephritis and prevented mortality in MRL-lpr mice. In summary, we show here that development of SLE-like kidney inflammation leads to a downregulation of the renal ILC2 response and identify an ILC2-expanding therapy as a promising treatment approach for autoimmune diseases.

Innate lymphoid cells in autoimmunity and chronic inflammatory diseases

Abnormal activation of the innate immune system is a common feature of autoimmune and chronic inflammatory diseases. Since their identification as a separate family of leukocytes, innate lymphoid cells (ILCs) have emerged as important effector cells of the innate immune system. Alterations in ILC function and subtype distribution have been observed in a variety of immune-mediated diseases in humans and evidence from experimental models suggests a subtype specific role of ILCs in the pathophysiology of autoimmune inflammation. In this review, we discuss recent advances in the understanding of ILC biology in autoimmune and chronic inflammatory disorders, including multiple sclerosis, inflammatory bowel diseases, psoriasis, and rheumatic diseases, with a special focus on the potential of ILCs as therapeutic targets for the development of novel treatment strategies in humans.

The therapeutic effect of anti-CD52 treatment in murine experimental autoimmune encephalomyelitis is associated with altered IL-33 and ST2 expression levels

Experimental autoimmune encephalomyelitis (EAE) mice were administered with murine anti-CD52 antibody to investigate its therapeutic effect and whether the treatment modulates IL-33 and ST2 expression. EAE severity and central nervous system (CNS) inflammation were reduced following the treatment, which was accompanied by peripheral T and B lymphocyte depletion and reduced production of various cytokines including IL-33, while sST2 was increased. In spinal cords of EAE mice, while the number of IL-33⁺ cells remained unchanged, the extracellular level of IL-33 protein was significantly reduced in anti-CD52 antibody treated mice compared with controls. Furthermore the number of ST2⁺ cells in the spinal cord of treated EAE mice was downregulated due to decreased inflammation and immune cell infiltration in the CNS. These results suggest that treatment with anti-CD52 antibody differentially alters expression of IL-33 and ST2, both systemically and within the CNS, which may indicate IL-33/ST2 axis is involved in the action of the antibody in inhibiting EAE.

IL-33/ST2 Pathway as a Rational Therapeutic Target for CNS Diseases

Interleukin (IL)-33 is a member of the interleukin-1 cytokine family that is produced by many different types of tissues including the central nervous system (CNS). IL-33 mediates its effects via its heterodimeric receptor complex, comprised of ST2 and the IL-1 receptor accessory protein (IL-1RAcp). As a pleiotropic nuclear cytokine, IL-33 is a crucial factor in the development of cardiovascular diseases, allergic diseases, infectious diseases, and autoimmune diseases. Recently, accumulated evidence shows that the IL-33/ST2 axis plays a crucial and diverse role in the pathogenesis of CNS diseases, including neurodegenerative diseases, cerebrovascular diseases, infectious diseases, traumatic CNS injury, chronic pain, etc. In this review, we discuss the recent findings in the cellular signaling of IL-33 and advancement of the role of IL-33 in several CNS diseases, as well as its therapeutic potential for the treatment of those diseases.

Tranilast inhibits interleukin-33 production by macrophages

Tranilast is an anti-allergy medication that inhibits the release of chemical mediators such as histamine. However, the mechanisms underlying its anti-allergy effects are not fully understood. Interleukin (IL)-33, a novel member of the IL-1 cytokine family, promotes T helper type 2 immune responses and plays a pathogenic role in allergic disorders. In the present study, we examined the effects of tranilast on IL-33 production by RAW264.7 macrophages. Lipopolysaccharide (LPS) increased both IL-33 mRNA expression and IL-33 protein synthesis. Tranilast significantly inhibited LPS-induced IL-33 protein production by RAW264.7 macrophages in a dose-dependent manner; these same effects were observed on IL-33 mRNA levels in RAW264.7 macrophages and a primary culture of macrophages. LPS markedly activated Akt in RAW264.7 macrophages, whereas tranilast suppressed LPS-induced Akt activation. The effects of tranilast on Akt activation appeared to be responsible for the decrease in IL-33 production. Our present findings suggest that the inhibition of IL-33 production by tranilast might contribute to the anti-allergy effects of this medication.

Interleukin-33 plasma levels in patients with relapsing-remitting multiple sclerosis

Cytokines are implicated in the immunopathogenesis of multiple sclerosis (MS). Interleukin (IL)-33, one of the recently discovered members of the IL-1 superfamily, is a dual functional cytokine involved in various autoimmune disorders. In a case-control study, venous blood was collected from healthy subjects categorized as control group (n=44) and MS patients (n=44). All recruited patients were clinically diagnosed with relapsing-remitting MS (RRMS), including patients without treatment (new identified cases, n=16) and those treated with interferon beta (IFN-β) (n=28). The plasma levels of IL-33 in subjects were measured with ELISA. Significantly elevated IL-33 plasma levels were observed in RRMS patients (p=0.005). Furthermore, IFN-β-treated MS patients had lower levels of IL-33 compared to the untreated patients (p<0.001). Increased IL-33 plasma levels in the patient group might be associated with development of MS. These results could contribute to our better understanding about the role of IL-33 in the immunopathogenesis of MS.

Murine Cytomegalovirus Infection Induces Susceptibility to EAE in Resistant BALB/c Mice

In contrast to C57BL/6 mice, BALB/c mice are relatively resistant to the induction of experimental autoimmune encephalomyelitis (EAE) after challenge with MOG_35–55 peptide. Here, we provide the first evidence that infection with murine cytomegalovirus (MCMV) in adulthood abrogates this resistance. Infected BALB/c mice developed clinical and histological signs similar to those seen in susceptible C57BL/6 mice. In addition to CD4⁺ cells, large proportion of cells in the infiltrate of diseased BALB/c mice was CD8⁺, similar with findings in multiple sclerosis. CD8⁺ cells that responded to ex vivo restimulation with MOG_35–55 were not specific for viral epitopes pp89 and m164. MCMV infection favors proinflammatory type of dendritic cells (CD86⁺CD40⁺CD11c⁺) in the peripheral lymph organs, M1 type of microglia in central nervous system, and increases development of Th1/Th17 encephalitogenic cells. This study indicates that MCMV may enhance autoimmune neuropathology and abrogate inherent resistance to EAE in mouse strain by enhancing proinflammatory phenotype of antigen-presenting cells, Th1/Th17, and CD8 response to MOG_35–55.

Innate lymphoid cells in autoimmunity: emerging regulators in rheumatic diseases

Innate lymphoid cells (ILCs) are important in the regulation of barrier homeostasis. These cells do not express T cell receptors but share many functional similarities with T helper cells and cytotoxic CD8⁺ T lymphocytes. ILCs are divided into three groups, namely group 1 ILCs, group 2 ILCs and group 3 ILCs, based on the transcription factors they depend on for their development and function, and the cytokines they produce. Emerging data indicate that ILCs not only have protective functions but can also have detrimental effects when dysregulated, leading to chronic inflammation and autoimmune diseases, including asthma, inflammatory bowel disease, graft-versus-host disease, psoriasis, rheumatoid arthritis and atopic dermatitis. Elucidation of the cytokine pathways involved in various autoimmune diseases - and the identification of ILCs as potent producers of these cytokines - points towards a potential role for these cellular players in the pathophysiology of these diseases. In this Review we discuss the current knowledge of the role of ILCs in the pathogenesis of rheumatic and other autoimmune diseases.

Matrine downregulates IL-33/ST2 expression in the central nervous system of rats with experimental autoimmune encephalomyelitis

Interleukin (IL)-33 is a recently described member of the IL-1 family and functions as a ligand for ST2, a member of the IL-1 receptor family. The role of IL-33/ST2 axis in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an experimental model of multiple sclerosis (MS), remains controversial. Matrine (MAT), a quinolizidine alkaloid derived from the herb Radix Sophorae Flave, has been recently found to suppress clinical EAE and CNS inflammation. However, the underlying immunoregulatory mechanisms have not been fully elucidated, and whether this effect of MAT is through inhibiting the function of the IL-33/ST2 axis is not known. In this study, we investigated the relationship between the therapeutic effects of MAT and IL-33/ST2 expression. MAT treatment successfully attenuated severe clinical deficit and histopathological changes, compared to untreated controls. While IL-33/ST2 mRNA expression was largely increased in spinal cord of EAE rats compared to naïve rats, this expression was significantly inhibited in rats treated with MAT. These results were further confirmed by their protein levels tested with immunohistochemistry. Together, our study demonstrates that MAT treatment regulates the inflammatory IL-33/ST2 axis, thus being a novel mechanism underlying the effect of MAT.

Role of IL-33 and ST2 signalling pathway in multiple sclerosis: expression by oligodendrocytes and inhibition of myelination in central nervous system

Recent research findings have provided convincing evidence indicating a role for Interleukin-33 (IL-33) signalling pathway in a number of central nervous system (CNS) diseases including multiple sclerosis (MS) and Alzheimer's disease. However, the exact function of IL-33 molecule within the CNS under normal and pathological conditions is currently unknown. In this study, we have mapped cellular expression of IL-33 and its receptor ST2 by immunohistochemistry in the brain tissues of MS patients and appropriate controls; and investigated the functional significance of these findings in vitro using a myelinating culture system. Our results demonstrate that IL-33 is expressed by neurons, astrocytes and microglia as well as oligodendrocytes, while ST2 is expressed in the lesions by oligodendrocytes and within and around axons. Furthermore, the expression levels and patterns of IL-33 and ST2 in the lesions of acute and chronic MS patient brain samples are enhanced compared with the healthy brain tissues. Finally, our data using rat myelinating co-cultures suggest that IL-33 may play an important role in MS development by inhibiting CNS myelination.

Increased Concentrations of Interleukin-33 in the Serum and Cerebrospinal Fluid of Patients with Multiple Sclerosis

OBJECTIVES

Interleukin (IL)-33 is a cytokine with both pro- and anti-inflammatory effects involved in the pathogenesis of some inflammatory diseases. The purpose of this investigation was to evaluate the serum and cerebrospinal fluid (CSF) IL-33 concentrations in patients with multiple sclerosis (MS).

METHODS

Blood specimens were obtained from 140 patients with MS (46 males and 94 females) with various disease patterns and treatment plans and 140 healthy subjects (47 males and 93 females), who acted as a control group. CSF samples were collected from 20 MS group and 20 sex- and age-matched patients with other neurological diseases of nonautoimmune etiology. The serum and CSF concentrations of IL-33 were measured by the enzyme-linked immunosorbent assay.

RESULTS

The serum and CSF IL-33 levels were significantly higher in the MS group compared to the control group (p<0.001 and p<0.050, respectively). The serum IL-33 concentrations were also significantly higher in newly diagnosed (untreated) patients and patients treated with methylprednisolone or with interferon-β and methylprednisolone compared to the healthy patient group (p<0.007, p<0.002, and p<0.010, respectively). Moreover, the serum IL-33 concentrations in patients with relapsing-remitting (RRMS), primary progressive (PPMS), and secondary progressive (SPMS) forms of the disease were significantly higher than in the healthy control group (p<0.006, p<0.001, and p<0.020, respectively).

CONCLUSIONS

Our results showed increased concentrations of IL-33 in patients with MS including both untreated and treated MS patients and patients with the RRMS, SPMS, and PPMS forms. This suggests that IL-33 may be involved in the pathogenesis of all MS forms and treatment with methylprednisolone or both interferon-β plus methylprednisolone has no influence on IL-33 concentrations.

Immunomodulation by interleukin-33 is protective in stroke through modulation of inflammation

Cerebral stroke induces massive Th1-shifted inflammation both in the brain and the periphery, contributing to the outcome of stroke. A Th1-type response is neurotoxic whereas a Th2-type response is accompanied by secretion of anti-inflammatory cytokines, such as interleukin-4 (IL-4). Interleukin-33 (IL-33) is a cytokine known to induce a shift towards the Th2-type immune response, polarize macrophages/microglia towards the M2-type, and induce production of anti-inflammatory cytokines. We found that the plasma levels of the inhibitory IL-33 receptor, sST2, are increased in human stroke and correlate with a worsened stroke outcome, suggesting an insufficient IL-33-driven Th2-type response. In mouse, peripheral administration of IL-33 reduced stroke-induced cell death and improved the sensitivity of the contralateral front paw at 5days post injury. The IL-33-treated mice had increased levels of IL-4 in the spleen and in the peri-ischemic area of the cortex. Neutralization of IL-4 by administration of an IL-4 antibody partially prevented the IL-33-mediated protection. IL-33 treatment also reduced astrocytic activation in the peri-ischemic area and increased the number of Arginase-1 immunopositive microglia/macrophages at the lesion site. In human T-cells, IL-33 treatment induced IL-4 secretion, and the conditioned media from IL-33-exposed T-cells reduced astrocytic activation. This study demonstrates that IL-33 is protective against ischemic insult by induction of IL-4 secretion and may represent a novel therapeutic approach for the treatment of stroke.

Group 2 innate lymphoid cells in disease

Group 2 innate lymphoid cells (ILC2) are now recognized as an important innate source of type-2 effector cytokines. Although initially associated with mucosal tissues, it is clear that ILC2 are present in diverse anatomical locations. The function of ILC2 at these sites is equally varied, and although ILC2 represent a relatively minor population, they are fundamentally important regulators of innate and adaptive immune processes. As such, there is much interest to understand the role of ILC2 in diseases with a type-2 inflammatory component. This review explores the known roles of ILC2 in disease, and the diseases that show associations or other strong evidence for the involvement of ILC2.

Altered Th17/Treg balance and dysregulated IL-1β response influence susceptibility/resistance to experimental autoimmune arthritis

This study was aimed at gaining an insight into immune mechanisms of differential susceptibility to autoimmunity of individuals sharing the same major histocompatibility complex by studying arthritis-susceptible Lewis (LEW) and arthritis-resistant Wistar Kyoto (WKY) rats (both RT.1(l)) using the adjuvant arthritis (AA) model of rheumatoid arthritis (RA). Lymph node cells (LNC) and synovium-infiltrating cells (SIC) of LEW and WKY rat subjected to an arthritogenic challenge were tested. The frequency of T helper 17 (Th17) and T regulatory (Treg) cells was determined by flow cytometry, whereas serum and spleen adherent cell (SAC)-derived supernatant were analyzed for specific cytokines and chemokines. We observed that WKY rats are not deficient in generating a Th17 response to the arthritogenic challenge in LNC (periphery); however, the Th17/Treg ratio is markedly reduced in the joint (target organ) of WKY versus LEW rats because of reduced Th17 levels therein in WKY rats. These results suggest differential and selective decrease in Th17 cell migration into the joints of WKY rats. Interestingly, serum levels of chemokines RANTES and MCP-1 were reduced in WKY rats. Furthermore, WKY rats showed reduced serum IL-1β level in vivo but no defect in IL-1β production by SAC in vitro, suggesting an effective in vivo regulation of IL-1β response. We also unraveled the role of interferon-γ (IFNγ), which we have previously reported to be increased in WKY versus LEW rats, in regulation of IL-1β. Thus, reduced Th17/Treg ratio in the target organ (joints) and decreased systemic IL-1β might contribute to the AA-resistance of WKY rats; whereas the converse factors render LEW more vulnerable to AA.

Differential Immunometabolic Phenotype in Th1 and Th2 Dominant Mouse Strains in Response to High-Fat Feeding

Immune reactivity plays an important role in obesity-associated metabolic disorders. We investigated immunometabolic phenotype of C57Bl/6 and BALB/c mice, prototypical Th1 and Th2-type strains, fed chow or high-fat diet (HFD) for 24 weeks. In comparison to C57Bl/6 mice, chow-fed BALB/c mice had higher body weight and weight gain, lower glycemia, more pronounced liver steatosis, but less inflammation and collagen deposition in liver. In response to HFD C57Bl/6 mice exhibited higher weight gain, higher glycemia, HbA1c and liver glycogen content, increased amount of visceral adipose tissue (VAT) and number of VAT associated CD3+CXCR3+ T cells, CD11c+ dendritic cells (DCs) and F4/80+ macrophages than BALB/c mice. More numerous CD3+ and CD8+ T lymphocytes, myeloid DCs, proinflammatory macrophages (F4/80+CD11b+CD11+ and F4/80+IL-1β+) and CD11b+Ly6Chigh monocytes and higher levels of proinflammatory IL-6, TNF-α and IFN-γ were present in liver in HFD-fed C57Bl/6 mice compared with diet-matched BALB/c mice. As opposed to C57Bl/6 mice, HFD induced marked liver steatosis and upregulated the hepatic LXRα and PPARγ genes in BALB/c mice. C57Bl/6 mice fed HFD developed liver fibrosis and increased hepatic procollagen and TGF-β mRNA expression, and IL-33, IL-13 and TGF-β levels in liver homogenates, while BALB/c mice fed HFD had scarce collagen deposition in liver. The obtained results suggest inherent immunometabolic differences in C57Bl/6 and BALB/c mice. Moreover, HFD Th1-type mice on high fat diet regimen are more susceptible to adiposity, liver inflammation and fibrosis, while Th2-type mice to liver steatosis, which is associated with differential immune cell composition in metabolic tissues. Strain-dependent differences in immunometabolic phenotype may be relevant for studies of obesity-associated metabolic diseases in humans.

Cutting edge: c-Kit signaling differentially regulates type 2 innate lymphoid cell accumulation and susceptibility to central nervous system demyelination in male and female SJL mice

Multiple sclerosis preferentially affects women, and this sexual dimorphism is recapitulated in the SJL mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). In this study, we demonstrate that signaling through c-Kit exerts distinct effects on EAE susceptibility in male and female SJL mice. Previous studies in females show that Kit mutant (W/W(v)) mice are less susceptible to EAE than are wild-type mice. However, male W/W(v) mice exhibit exacerbated disease, a phenotype independent of mast cells and corresponding to a shift from a Th2- to a Th17-dominated T cell response. We demonstrate a previously undescribed deficit in c-Kit(+) type 2 innate lymphoid cells (ILC2s) in W/W(v) mice. ILC2s are also significantly reduced in EAE-susceptible wild-type females, indicating that both c-Kit signals and undefined male-specific factors are required for ILC2 function. We propose that deficiencies in Th2-promoting ILC2s remove an attenuating influence on the encephalitogenic T cell response and therefore increases disease susceptibility.

Expression of interleukin-33 and its receptor ST2 in periapical granulomas and radicular cysts

BACKGROUND

Interleukin-33 (IL-33) is a recently identified cytokine belonging to the IL-1 family and ligand for the IL-1 receptor-related protein ST2. IL-33/ST2 signaling plays a critical role in allergy, autoimmunity, and chronic inflammatory disorders, but its role in the pathogenesis of periapical lesions is unknown. We aimed to investigate the expression patterns of IL-33 and ST2 in human periapical lesions.

METHODS

Periapical lesions (n = 36) and healthy periapical tissues (n = 10) were evaluated by immunohistochemistry using antibodies specific for human IL-33 and ST2. Lesion samples were further analyzed by double immunofluorescence to assess IL-33/ST2 co-expression.

RESULTS

The numbers of IL-33- and ST2-positive fibroblasts were significantly higher in periapical lesions compared to healthy periapical tissues (both P < 0.05), while the numbers of IL-33- and ST2-positive endothelial cells were similar (both P > 0.05). There were no significant differences in the numbers of IL-33- and ST2-positive fibroblasts and endothelial cells between periapical granulomas and radicular cysts (all P > 0.05). Similarly, numbers of ST2-positive mononuclear cells did not differ between periapical granulomas and radicular cysts (P > 0.05). The majority of epithelial cells in radicular cysts were IL-33 positive, while the small proportion of epithelial cells was ST2 positive. Double immunofluorescence analysis revealed IL-33/ST2 co-expression in fibroblasts and endothelial cells.

CONCLUSIONS

IL-33 and ST2 are expressed in periapical granulomas and radicular cysts. Increased numbers of IL-33- and ST2-positive fibroblasts in periapical lesions when compared to healthy periapical tissues suggest that IL-33/ST2 signaling may be involved in periapical inflammation and tissue fibrosis.

ST2 deletion increases inflammatory bone destruction in experimentally induced periapical lesions in mice

INTRODUCTION

ST2 is a member of the interleukin (IL)-1 receptor family, and IL-33 is its natural ligand. ST2 signaling promotes Th2 immune response in allergy, autoimmunity, and chronic inflammatory disorders, but its role in the pathogenesis of periapical lesions is unknown. The purpose of this study was to investigate whether ST2 gene deletion affects the development of experimentally induced periapical lesions in mice.

METHODS

Pulps of mandibular molars from wild-type (WT) and ST2 knockout (ST2(-)/(-)) BALB/c mice were exposed and left open to the oral environment. After death, hemi-mandibles were isolated and prepared for histologic, immunohistochemical, and flow cytometric analysis.

RESULTS

The expression of IL-33 and its receptor ST2 was higher in periapical lesions in WT mice compared with normal root apices (both P < .05). The increased periapical bone loss observed in ST2(-)/(-) mice was associated with enhanced influx of neutrophils, CD3+ CXCR3+ Th1 cells, and CD3+ CCR6+ Th17 cells and increased number of tartrate-resistant acid phosphatase+ osteoclasts (all P < .05). Furthermore, periapical lesions in ST2(-)/(-) mice contained increased percentages of T cells expressing interferon-γ, IL-17, tumor necrosis factor-α, and IL-6 (all P < .05). In comparison with WT mice, CD3+ receptor activator of nuclear factor kappa B ligand+ T cells were increased, whereas CD3+ osteoprotegerin+ T cells were decreased in the lesions of ST2(-)/(-) mice (both P < .05).

CONCLUSIONS

ST2 deletion increases inflammatory bone loss in experimental periapical lesions in mice, which is associated with enhanced Th1/Th17 cell mediated periapical immune responses and increased osteoclastogenesis.

Ginger extracts influence the expression of IL-27 and IL-33 in the central nervous system in experimental autoimmune encephalomyelitis and ameliorates the clinical symptoms of disease

The immunomodulatory effects of the IL-27 and IL-33 and the anti-inflammatory effects of ginger have been reported in some studies. The aim was to evaluate the effects of the ginger extract on the expression of IL-27 and IL-33 in a model of experimental autoimmune encephalomyelitis (EAE). In PBS-treated EAE mice the expression of IL-27 P28 was significantly lower whereas the expression of IL-33 was significantly higher than unimmunized control mice. In 200 and 300 mg/kg ginger-treated EAE groups the expression of IL-27 P28 and IL-27 EBI3 was significantly higher whereas the expression of IL-33 was significantly lower than PBS-treated EAE mice. The EAE clinical symptoms and the pathological scores were significantly lower in ginger-treated EAE groups. These results showed that the ginger extract modulates the expression of the IL-27 and IL-33 in the spinal cord of EAE mice and ameliorates the clinical symptoms of disease.

The in vivo and in vitro induction of anterior chamber associated immune deviation to myelin antigens in C57BL/6 mice

Introduction of antigens into the anterior chamber (AC) of the eye generates a specific systemic form of tolerance that is termed AC-associated immune deviation (ACAID). Experimental autoimmune encephalomyelitis (EAE) is an animal model of the human CNS demyelinating diseases, including multiple sclerosis (MS) and acute disseminated encephalomyelitis. We investigated whether the encephalitogenic antigens myelin oligodendrocyte glycoprotein (MOG35-55) or myelin basic protein (MBP) induce ACAID in the EAE-prone C57BL/6 mice. We hypothesized that injection of MOG35-55/MBP induces antigen-specific tolerance whether via the AC route, the adoptive transfer of in vitro-generated MOG35-55-specific/MBP-specific ACAID antigen presenting cells (APCs), or the adoptive transfer of MOG35-55-specific/MBP-specific ACAID T regulatory cells (Tregs). ACAID is characterized by the specific impairment of delayed-type hypersensitivity (DTH) responses. Thus, DTH assays were used to test for ACAID following the AC injection of MOG35-55/MBP, or the intravenous injection of MOG35-55-specific/MBP-specific ACAID APCs. The functional local adoptive transfer (LAT) assays were used to examine the putative regulatory functions of in vitro generated MOG35-55-specific/MBP-specific Tregs. This report is the first to demonstrate the in vivo and in vitro induction of MOG35-55-specific/MBP-specific ACAID-mediated tolerance in C57BL/6 mice. These findings highlight the need for novel immunotherapeutic strategies for MS and optic neuritis.

Role of IL-33 and its receptor in T cell-mediated autoimmune diseases

Interleukin-33 (IL-33) is a new cytokine of interleukin-1 family, whose specific receptor is ST2. IL-33 exerts its functions via its target cells and plays different roles in diseases. ST2 deletion and exclusion of IL-33/ST2 axis are accompanied by enhanced susceptibility to dominantly T cell-mediated organ-specific autoimmune diseases. It has been reported that IL-33/ST2 pathway plays a key role in host defense and immune regulation in inflammatory and infectious diseases. This review focuses on new findings in the roles of IL-33 and ST2 in several kinds of T cell-mediated autoimmune diseases.