A role for TSLP in the development of inflammation in an asthma model

Critical role of TSLP-responsive mucosal dendritic cells in the induction of nasal antigen-specific IgA response

Thymic stromal lymphopoietin (TSLP) is an interleukin-7 (IL-7)-like cytokine involved in T helper 2 type immune responses. The primary target of TSLP is myeloid dendritic cells (DCs), however, little is known about the mechanism by which TSLP elicits respiratory IgA immune responses upon mucosal immunization. Here, we found that the levels of TSLP and TSLPR were upregulated in the mucosal DCs of mice nasally immunized with pneumococcal surface protein A (PspA) plus cholera toxin (CT) compared with those immunized with PspA alone. PspA-specific IgA responses, but not IgG Ab responses were significantly reduced in both serum and mucosal secretions of TSLPR knockout mice compared with wild-type mice after nasal immunization with PspA plus CT. Furthermore, CD11c⁺ mucosal DCs isolated from TSLPR knockout mice nasally immunized with PspA plus CT were less activated and exhibited markedly reduced expression of IgA-enhancing cytokines (e.g., APRIL, BAFF, and IL-6) compared with those from equivalently immunized wild-type mice. Finally, exogenous TSLP promoted production of IgAs in an in vitro DC-B cell co-culture system as exhibited by enhanced IL-6 production. These results suggest that TSLP-TSLPR signaling is pivotal in the induction of nasal respiratory immunity against pathogenic pneumococcal infection.

New perspectives on the regulation of type II inflammation in asthma

Asthma is a chronic inflammatory disease of the lungs which has been thought to arise as a result of inappropriately directed T helper type-2 (Th2) immune responses of the lungs to otherwise innocuous inhaled antigens. Current asthma therapeutics are directed towards the amelioration of downstream consequences of type-2 immune responses (i.e. β-agonists) or broad-spectrum immunosuppression (i.e. corticosteroids). However, few approaches to date have been focused on the primary prevention of immune deviation. Advances in molecular phenotyping reveal heterogeneity within the asthmatic population with multiple endotypes whose varying expression depends on the interplay between numerous environmental factors and the inheritance of a broad range of susceptibility genes. The most common endotype is one described as "type-2-high" (i.e. high levels of interleukin [IL]-13, eosinophilia, and periostin). The identification of multiple endotypes has provided a potential explanation for the observations that therapies directed at typical Th2 cytokines (IL-4, IL-5, and IL-13) and their receptors have often fallen short when they were tested in a diverse group of asthmatic patients without first stratifying based on disease endotype or severity. However, despite the incorporation of endotype-dependent stratification schemes into clinical trial designs, variation in drug responses are still apparent, suggesting that additional genetic/environmental factors may be contributing to the diversity in drug efficacy. Herein, we will review recent advances in our understanding of the complex pathways involved in the initiation and regulation of type-2-mediated immune responses and their modulation by host factors (genetics, metabolic status, and the microbiome). Particular consideration will be given to how this knowledge could pave the way for further refinement of disease endotypes and/or the development of novel therapeutic strategies for the treatment of asthma .

HIV-Tat regulates macrophage gene expression in the context of neuroAIDS

Despite the success of cART, greater than 50% of HIV infected people develop cognitive and motor deficits termed HIV-associated neurocognitive disorders (HAND). Macrophages are the major cell type infected in the CNS. Unlike for T cells, the virus does not kill macrophages and these long-lived cells may become HIV reservoirs in the brain. They produce cytokines/chemokines and viral proteins that promote inflammation and neuronal damage, playing a key role in HIV neuropathogenesis. HIV Tat is the transactivator of transcription that is essential for replication and transcriptional regulation of the virus and is the first protein to be produced after HIV infection. Even with successful cART, Tat is produced by infected cells. In this study we examined the role of the HIV Tat protein in the regulation of gene expression in human macrophages. Using THP-1 cells, a human monocyte/macrophage cell line, and their infection with lentivirus, we generated stable cell lines that express Tat-Flag. We performed ChIP-seq analysis of these cells and found 66 association sites of Tat in promoter or coding regions. Among these are C5, CRLF2/TSLPR, BDNF, and APBA1/Mint1, genes associated with inflammation/damage. We confirmed the association of Tat with these sequences by ChIP assay and expression of these genes in our THP-1 cell lines by qRT-PCR. We found that HIV Tat increased expression of C5, APBA1, and BDNF, and decreased CRLF2. The K50A Tat-mutation dysregulated expression of these genes without affecting the binding of the Tat complex to their gene sequences. Our data suggest that HIV Tat, produced by macrophage HIV reservoirs in the brain despite successful cART, contributes to neuropathogenesis in HIV-infected people.

TSLP signaling blocking alleviates E-cadherin dysfunction of airway epithelium in a HDM-induced asthma model

Recent studies have indicated that Thymic stromal lymphopoietin (TSLP) plays an important role in the prevention and treatment of asthma. However the role of TSLP in dysfunction of airway epithelial adherens junctions E-cadherin in house dust mite (HDM)-induced asthma has not been addressed. We hypothesized that TSLP contributed to HDM-induced E-cadherin dysfunction in asthmatic BALB/c mice and 16HBE cells. In vivo, a HDM-induced asthma mouse model was set up for 8weeks. Mice inhaled an anti-TSLP monoclonal antibody (mAb) before HDM. The mice treated with the anti-TSLP mAb ameliorated airway inflammation, the decreasing and aberrant distribution of E-cadherin and β-catenin as well as phosphorylation(p)-AKT induced by HDM. In vitro, HDM increased the expression of TSLP and E-cadherin dysfunction by PI3K/Akt signaling pathway. The exposure of 16HBE to TSLP resulted in redistribution of E-cadherin. These results indicate that TSLP may be an important contributor in E-cadherin dysfunction of HDM-induced asthma. TSLP signaling blocking shows a protective effect in mice and that the PI3K/Akt pathway may play a role in this process.

Upregulation of interleukin-33 and thymic stromal lymphopoietin levels in the lungs of idiopathic pulmonary fibrosis

BACKGROUND

Innate T helper type 2 (Th2) immune responses mediated by interleukin (IL)-33, thymic stromal lymphopoietin (TSLP), and IL-25 have been shown to play an important role in pulmonary fibrosis of animal models; however, their clinical implications remain poorly understood.

METHODS

TSLP, IL-25, and IL-33 concentrations were measured in bronchoalveolar lavage fluids obtained from normal controls (NCs; n = 40) and from patients with idiopathic pulmonary fibrosis (IPF; n = 100), non-specific interstitial pneumonia (NSIP; n = 22), hypersensitivity pneumonitis (HP; n = 20), and sarcoidosis (n = 19).

RESULTS

The TSLP and IL-33 levels were significantly higher in patients with IPF relative to the NCs (p = 0.01 and p = 0.0001, respectively), NSIP (p = 4.95E - 7 and p = 0.0002, respectively), HP (p = 0.00003 and p = 0.000005, respectively), and sarcoidosis groups (p = 0.003 and p = 0.0001, respectively). However, the IL-25 levels were not significantly different between NC and IPF group (p = 0.432). Receiver operating characteristic curves of the TSLP and IL-33 levels revealed clear differences between the IPF and NC groups (AUC = 0.655 and 0.706, respectively), as well as between the IPF and the other lung disease groups (AUC = 0.786 and 0.781, respectively). Cut-off values of 3.52 pg/μg TSLP and 3.77 pg/μg IL-33 were shown to differentiate between the IPF and NC groups with 99.2 and 94.3% accuracy. Cut-off values of 4.66 pg/μg TSLP and 2.52 pg/μg IL-33 possessed 99.4 and 93.2% accuracy for differentiating among the IPF and other interstitial lung disease groups.

CONCLUSIONS

Innate immune responses may be associated with the development of IPF. Furthermore, the IL-33 and TSLP levels in BAL fluids may be useful for differentiating IPF from other chronic interstitial lung diseases.

Distinct roles of short and long thymic stromal lymphopoietin isoforms in house dust mite-induced asthmatic airway epithelial barrier disruption

Loss of airway epithelial integrity contributes significantly to asthma pathogenesis. Thymic stromal lymphopoietin (TSLP) may have dual immunoregulatory roles. In inflammatory disorders of the bowel, the long isoform of TSLP (lfTSLP) promotes inflammation while the short isoform (sfTSLP) inhibits inflammation. We hypothesize that lfTSLP contributes to house dust mite (HDM)-induced airway epithelial barrier dysfunction and that synthetic sfTSLP can prevent these effects. In vitro, airway epithelial barrier function was assessed by monitoring transepithelial electrical resistance, fluorescent-dextran permeability, and distribution of E-cadherin and β-catenin. In vivo, BALB/c mice were exposed to HDM by nasal inhalation for 5 consecutive days per week to establish an asthma model. sfTSLP and 1α,25-Dihydroxyvitamin D3 (1,25D3) were administered 1 h before HDM exposure. After 8 weeks, animal lung function tests and pathological staining were performed to evaluate asthma progression. We found that HDM and lfTSLP impaired barrier function. Treatment with sfTSLP and 1,25D3 prevented HDM-induced airway epithelial barrier disruption. Moreover, sfTSLP and 1,25D3 treatment ameliorated HDM-induced asthma in mice. Our data emphasize the importance of the different expression patterns and biological properties of sfTSLP and lfTSLP. Moreover, our results indicate that sfTSLP and 1,25D3 may serve as novel therapeutic agents for individualized treatment of asthma.

Th2 Cells and Th17 Cells in the Development of Endometriosis – Possible Roles of Interleukin-4 and Interleukin-17A

Endometriosis is recognized as an inflammatory disease in which inflammatory cytokines, such as interleukin (IL)-1β and TNFα, play important roles. Immunological factors are also suggested to be involved in the pathogenesis of endometriosis. This review provides comprehensive knowledge about helper T cell (Th cell) and its specific cytokines in endometriosis. A series of our studies demonstrated the presence of Th2 cells and Th17 cells in endometriotic tissues and revealed multiple effects of IL-4 and IL-17A, cytokines secreted from respective Th cells. IL-1β induces secretion of thymic stromal lymphopoietin (TSLP), a regulator for differentiation of inflammatory Th2 cells, in endometriotic stromal cells (ESCs). IL-4 stimulates proliferation of ESCs and production of 3β-hydroxysteroid dehydrogenase Type 2, an enzyme in an estrogen production pathway, in ESCs. IL-17A stimulates IL-8 and Gro-α secretion from ESCs and proliferation of ESCs. IL-17A-induced Gro-α promotes neutrophil migration, which may contribute to the presence of neutrophils in endometriotic tissues. IL-17A also increases secretion of CCL20, a chemokine for Th17 cells, from ESCs, which seems to induce migration of Th17 cells to the endometriotic tissues and enhance the effects of IL-17A further. TNFα in combination with IL-17A synergistically enhances secretion of IL-8 and CCL-20, suggesting cooperation of inflammation and Th17 immune response. These findings suggest that IL-4 and IL-17A promote the development of endometriosis through induction of cell proliferation, inflammation, and estrogen production. It is thus also suggested that IL-4 and IL-17A would be a target of treatment of the disease.

A TSLP-complement axis mediates neutrophil killing of methicillin-resistant Staphylococcus aureus

Community-acquired Staphylococcus aureus infections often present as serious skin infections in otherwise healthy individuals and have become a worldwide epidemic problem fueled by the emergence of strains with antibiotic resistance, such as methicillin-resistant S. aureus (MRSA). The cytokine thymic stromal lymphopoietin (TSLP) is highly expressed in the skin and in other barrier surfaces and plays a deleterious role by promoting T helper cell type 2 (TH2) responses during allergic diseases; however, its role in host defense against bacterial infections has not been well elucidated. We describe a previously unrecognized non-TH2 role for TSLP in enhancing neutrophil killing of MRSA during an in vivo skin infection. Specifically, we demonstrate that TSLP acts directly on both mouse and human neutrophils to augment control of MRSA. Additionally, we show that TSLP also enhances killing of Streptococcus pyogenes, another clinically important cause of human skin infections. Unexpectedly, TSLP mechanistically mediates its antibacterial effect by directly engaging the complement C5 system to modulate production of reactive oxygen species by neutrophils. Thus, TSLP increases MRSA killing in a neutrophil- and complement-dependent manner, revealing a key connection between TSLP and the innate complement system, with potentially important therapeutic implications for control of MRSA infection.

Epithelial-Derived Cytokines in Asthma

The interaction between the airway epithelium and the inhaled environment is crucial to understanding the pathobiology of asthma. Several studies have identified an important role of airway epithelial-derived cytokines, IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) in asthma pathogenesis. These cytokines have been described as epithelial-derived alarmins that activate and potentiate the innate and humoral arms of the immune system in the presence of actual or perceived damage. Each of the three epithelial-derived alarmins has been implicated in the pathobiology of inhaled allergen-induced airway responses. The best evidence to date exists for TSLP, in that a human monoclonal antibody, which binds TSLP and prevents its engagement with its receptor, resolves airway inflammation in patients with allergic asthma and attenuates allergen-induced airway responses. Better understanding the roles that the epithelial-derived alarmins play and how they influence airway immune response may allow the development of novel therapeutics for asthma treatment.

Lipopolysaccharide Attenuates Induction of Proallergic Cytokines, Thymic Stromal Lymphopoietin, and Interleukin 33 in Respiratory Epithelial Cells Stimulated with PolyI:C and Human Parechovirus

Epidemiological studies based on the "hygiene hypothesis" declare that the level of childhood exposure to environmental microbial products is inversely related to the incidence of allergic diseases in later life. Multiple types of immune cell-mediated immune regulation networks support the hygiene hypothesis. Epithelial cells are the first line of response to microbial products in the environment and bridge the innate and adaptive immune systems; however, their role in the hygiene hypothesis is unknown. To demonstrate the hygiene hypothesis in airway epithelial cells, we examined the effect of lipopolysaccharide (LPS; toll-like receptor 4 ligand) on the expression of the proallergic cytokines thymic stromal lymphopoietin (TSLP) and interleukin 33 (IL33) in H292 cells (pulmonary mucoepidermoid carcinoma cells). Stimulation with the TLR ligand polyI:C and human parechovirus type 1 (HPeV1) but not LPS-induced TSLP and IL33 through interferon regulatory factor 3 (IRF3) and NF-κB activity, which was further validated by using inhibitors (dexamethasone and Bay 11-7082) and short hairpin RNA-mediated gene knockdown. Importantly, polyI:C and HPeV1-stimulated TSLP and IL33 induction was reduced by LPS treatment by attenuating TANK-binding kinase 1, IRF3, and NF-κB activation. Interestingly, the basal mRNA levels of TLR signaling proteins were downregulated with long-term LPS treatment of H292 cells, which suggests that such long-term exposure modulates the expression of innate immunity signaling molecules in airway epithelial cells to mitigate the allergic response. In contrast to the effects of LPS treatment, the alarmin high-mobility group protein B1 acts in synergy with polyI:C to promote TSLP and IL33 expression. Our data support part of the hygiene hypothesis in airway epithelia cells in vitro. In addition to therapeutic targeting of TSLP and IL33, local application of non-pathogenic LPS may be a rational strategy to prevent allergies.

TSLP receptor is not essential for house dust mite-induced allergic rhinitis in mice

TSLP induces Th2 cytokine production by Th2 cells and various other types of cells, thereby contributing to Th2-type immune responses and development of allergic disorders. We found that house dust mite (HDM) extract induced TSLP production by nasal epithelial cells, suggesting that TSLP may be involved in development of HDM-induced allergic rhinitis (AR). To investigate that possibility in greater detail, wild-type and TSLP receptor-deficient (TSLPR-/-) mice on the C57BL/6J background were repeatedly treated intranasally with HDM extract. The frequency of sneezing, numbers of eosinophils and goblet cells, thickness of submucosal layers, serum levels of total IgE and HDM-specific IgG1, and levels of IL-4, IL-5 and IL-13 in the culture supernatants of HDM-stimulated LN cells were comparable in the two mouse strains. Those findings indicate that, in mice, TSLPR is not crucial for development of HDM-induced AR.

Interleukin-4- and NACHT, LRR and PYD domains-containing protein 3-independent mechanisms of alum enhanced T helper type 2 responses on basophils

Aluminium hydroxide (alum), the most widely used adjuvant in human and animal vaccines, has long been known to promote T helper type 2 (Th2) responses and Th2-associated humoral responses, but the mechanisms have remained poorly understood. In this study, we explored whether alum is able to directly modulate antigen-presenting cells to enhance their potency for Th2 polarization. We found that alum treatment of dendritic cells failed to show any Th2-promoting activities. In contrast, alum was able to enhance the capacity of basophils to induce Th2 cells. When basophils from interleukin-4 (IL-4) knockout mice were examined, the intrinsic Th2-promoting activities by basophils were largely abrogated, but the alum-enhanced Th2-promoting activities on basophils were still detectable. More importantly, Th2-promoting adjuvant activities by alum found in IL-4 knockout mice were also largely reduced when basophils were depleted by antibody administration. Therefore, basophils can mediate Th2-promoting activities by alum both in vitro and in vivo through IL-4-independent mechanisms. Further studies revealed that secreted soluble molecules from alum-treated basophils were able to confer the Th2-promoting activities, and neutralization of thymic stromal lymphopoietin or IL-25 attenuated the IL-4-independent development of Th2 cells elicited by alum-treated basophils. Finally, alum was able to activate NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome in murine basophils in the same way as alum in professional antigen-presenting cells, but NLRP3 was not required for Th2-promoting activities on basophils by alum in vitro. These results demonstrated that alum can enhance the capacities of basophils to polarize Th2 cells via IL-4- and NLRP3-independent pathways.

Treatment with cytokine thymic stromal lymphopoietin short hairpin RNA substantially reduces TGF-β1-induced interstitial cellular fibrosis

Thymic stromal lymphopoietin (TSLP) has previously been linked to allergic inflammatory diseases, and tissue fibrosis and organ dysfunction may also arise from such inflammation. It remains unclear, however, whether TSLP plays any role in the occurrence of renal fibrosis, so this study investigated that possibility. An in vitro fibrosis model was established by treating normal rat kidney fibroblast (NRK-49F) cells with transforming growth factor-β1 (TGF-β1), after which the levels of various fibrogenic markers (e.g., fibronectin) and downstream fibrogenic signal proteins (e.g., smad 7) were investigated. Also, TSLP shRNA was used to silence the effects of TSLP, while an ELISA was conducted to evaluate the fibronectin secretions. The level of fibronectin in the NRK-49F cells was dose- and time-dependently increased by the administration of exogenous TSLP (P<0.05). TSLP also significantly increased the level of fibrosis signaling, in addition to inducing a marked decrease in the down-regulation of Smad7. Interestingly, the application of TSLP shRNA caused a stark reversal of the TGF-β1-induced cellular fibrosis while simultaneously leading to the suppression of fibronectin and fibrogenic signal proteins. Taken together, these observations provide insights into how extracellular matrices develop and could thus lead to potential therapeutic interventions for the suppression of renal fibrosis.

Thymic Stromal Lymphopoietin Neutralization Inhibits the Immune Adjuvant Effect of Di-(2-Ethylhexyl) Phthalate in Balb/c Mouse Asthma Model

Di-(2-ethylhexyl) phthalate (DEHP), a commonly used plasticizer, has an adjuvant effect in combination with ovalbumin (OVA). The adjuvant effect of DEHP has already been verified in our previous studies. In this study, to further investigate whether thymic stromal lymphopoietin (TSLP) was involved in the DEHP-adjuvant effect, DEHP was administered through a daily gavage exposure route. Mice were sensitized with ovalbumin (OVA) to trigger allergic responses, and an anti-TSLP monoclonal antibody was used to neutralize the effect of TSLP. Biomarkers including cytokines in bronchoalveolar lavage fluid (BALF), serum total IgE and TSLP content in the lung were detected. In addition, airway hyperreactivity and lung sections were examined. Collectively, these data indicated a salient Th2 response which was characterized by the upregulation of Th2-type cytokines, such as interleukin 4 (IL-4), IL-5 and IL-13. Moreover, the eosinophil number in BALF and the eosinophil cationic protein (ECP) in the lung were seen to have increased significantly. However, neutralization of TSLP with an anti-TSLP mAb reversed the adjuvant effect of DEHP on airway inflammation, structural alterations in the airway wall and increased airway hyperresponsiveness (AHR) to methacholine induced by the OVA allergen, suggesting that TSLP was an effective target site for suppressing the adjuvant effect of DEHP co-exposure.

Direct versus sequential immunoglobulin switch in allergy and antiviral responses

Allergy is characterized by IgE production to innocuous antigens. The question whether the switch to IgE synthesis occurs via direct or sequential pathways is still unresolved. The aim of this work was to analyze the distribution of immunoglobulins (Ig) to house dust mite D. farinae and A. alternata fungus in allergic children with primarily established diagnosis and compare it to Epstein-Barr antiviral (EBV) response in the same patients. In allergy patients the only significant difference was found in allergen specific IgE, likely mediated by a direct isotype switch, while antiviral response was dominated by EBV specific IgG and low level of concordant IgA and IgG4 production consistent with a minor sequential Ig switches. Taken collectively, we concluded that sequential isotype switch is likely to be a much rarer event than a direct one.

Aberrant Expression of Novel Cytokine IL-38 and Regulatory T Lymphocytes in Childhood Asthma

We investigated the expression of novel anti-inflammatory interleukin (IL)-38 and regulatory T (Treg) lymphocytes in childhood asthma patients. The protein and mRNA expression level of IL-38, periostin, peripheral CD4⁺CD25⁺CD134⁺ T lymphocytes as well as CD4⁺CD25(high)FoxP3⁺ and CD4⁺CD25(high)CD127(-) Treg lymphocytes from 40 asthmatic patients and 20 normal control (NC) subjects were studied using ELISA, qPCR and flow cytometry. Serum and supernatant cytokines/chemokines were determined by multiplex assay. Serum IL-38, IL-5, IL-17, IL-6, interferon-γ, periostin, IL-1β and IL-13 concentrations were significantly higher in asthmatic patients with or without steroid treatment than those in controls (all p < 0.05). The percentages of both CD4⁺CD25(high)FoxP3⁺ and CD4⁺CD25(high)CD127(-) Treg lymphocytes were markedly decreased in asthmatic patients with and without steroid treatment than those in controls (all p < 0.05). The elevated IL-38 concentration negatively correlated with the percentage of Treg lymphocytes in asthmatic patients with high level (>40 ng/mL) of periostin (p < 0.05). Although the comparable mRNA levels of IL-38 and its receptor IL-36R were found between patients and controls, the mRNA level of IL-38 positively correlated with IL-36R and negatively correlated with IL-10 in all asthmatic patients (both p < 0.05). The percentage of CD4⁺CD25⁺CD134⁺ activated T lymphocytes was also significantly higher in asthmatic patients with steroid treatment than those in controls (p < 0.05). This cross-sectional study demonstrated that the overexpression of circulating IL-38 may play a role in the immunopathogenesis in asthma.

From genetics to treatment of eosinophilic esophagitis

PURPOSE OF REVIEW

Eosinophilic Esophagitis (EoE) is an emerging chronic atopic disease. Recent advances in understanding its genetic and molecular biology pathogenesis may lead to a better management of the disease

RECENT FINDINGS

EoE is an atopic disease. Most of the patients affected by EoE have other atopic diseases such as allergic rhinitis, asthma, IgE-mediated food allergies and/or atopic dermatitis. The local inflammation is a T helper type 2 (Th2) flogosis, which most likely is driven by a mixed IgE and n-IgE-mediated reaction to food and/or environmental allergens. Epidemiological studies show that EoE is an atopic disease with a strong genetic component. Genetic studies have shown that EoE is associated with single nucleotide polymorphism on genes, which are released by the epithelium and important in atopic inflammation such as thymic stromal lymphopoietin located (TSLP) close to the Th2 cytokine cluster [interleukin (IL)-4, IL-5, IL-13] on chromosome 5q22, Calpain 14, EMSY, and Eotaxin3. When the EoE diagnosis is made, it is imperative to control the local eosinophilic inflammation not only to give symptomatic relief to the patient, but also to prevent complications such as esophageal stricture and food impaction.

SUMMARY

EoE is treated like many other atopic diseases with a combination of topical steroids and/or food antigen avoidance. The new understanding of EoE may lead to more specific and definitive treatments of EoE.

The Therapeutic Potential of Targeting Cytokine Alarmins to Treat Allergic Airway Inflammation

Asthma is a heterogeneous disorder that results in recurrent attacks of breathlessness, coughing, and wheezing that affects millions of people worldwide. Although the precise causes of asthma are unclear, studies suggest that a combination of genetic predisposition and environmental exposure to various allergens and pathogens contribute to its development. Currently, the most common treatment to control asthma is a dual combination of β2-adrenergic receptor agonists and corticosteroids. However, studies have shown that some patients do not respond well to these medications, while others experience significant side effects. It is reported that the majority of asthmas are associated with T helper type 2 (TH2) responses. In these patients, allergen challenge initiates the influx of TH2 cells in the airways leading to an increased production of TH2-associated cytokines and the promotion of allergy-induced asthma. Therefore, biologics that target this pathway may provide an alternative method to treat the allergic airway inflammation associated with asthma. As of now, only two biologics (omalizumab and mepolizumab), which target immunoglobulin E and interleukin-5, respectively, are FDA-approved and being prescribed to asthmatics. However, recent studies have reported that targeting other components of the TH2 response also show great promise. In this review, we will briefly describe the immunologic mechanisms underlying allergic asthma. Furthermore, we will discuss the current therapeutic strategies used to treat asthma including their limitations. Finally, we will highlight the benefits of using biologics to treat asthma-associated allergic airway inflammation with an emphasis on the potential of targeting cytokine alarmins, especially thymic stromal lymphopoietin.

Upregulated thymic stromal lymphopoietin receptor expression in children with asthma

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays an important role in pathogenesis in patients with asthma. However, the role of thymic stromal lymphopoietin receptor (TSLPR) and correlation with IL-7Rα and clinical severity in asthmatic or nonasthmatic children remain unclear. We investigated TSLPR and IL-7Rα mRΝΑ levels in asthma and nonasthma and assessed TSLPR expression in children who were sensitive to mites.

MATERIALS AND METHODS

We enrolled asthmatic and nonasthmatic children. To minimize the influence of allergy, we also divided participants into following 4 groups: nonallergic and nonasthmatic group (NN) (healthy children), allergic but nonasthmatic group (AN), nonallergic but asthmatic group (NA) and allergic asthmatic group (AA). We drew blood samples to check total IgE, allergen-specific IgE and TSLP and measured the expression of the TSLPR and IL-7Rα genes using reverse-transcription polymerase chain reaction (RT-PCR) and real-time PCR. Asthma symptom score was also recorded.

RESULTS

Thymic stromal lymphopoietin and TSLPR levels were found to be significantly higher in asthmatic than in nonasthmatic children. The levels of TSLP were found to be significantly different between AA and NN groups (P < 0·05). TSLPR expression in NA and AA groups was found to be significantly higher than in NN group (P < 0·05). TSLPR did not differ significantly between NA and AA groups. The TSLPR expression correlated strongly with IL-7Rα and weakly with mite-specific IgE. Clinical asthmatic severity of children was found to exert no influence on TSLPR level.

CONCLUSION

Thymic stromal lymphopoietin receptor might be a significant disease biomarker for asthma. The levels of TSLPR were found to be higher in asthmatic patients than in healthy children, but were found to be not different between allergic and nonallergic asthmatic patients.

It is time to beelieve the CD1a hype!

Conventional T cells have historically been linked to exacerbating allergy. By efficiently generating primarily TH 2 cells, allergens skew the immune response to produce IL-4, IL-13, and IgE. Previously, CD1a-responsive T cells were shown to functionally respond to bee and wasp venom allergens. In this issue of the European Journal of Immunology, Subramaniam et al. [Eur. J. Immunol. 2016. 46: 242-252] show that more functionally active CD1a-restricted cells are present in bee venom-allergic patients than in healthy patients. Additionally, the authors show that these cells are not as frequently found in individuals receiving venom immunotherapy. Consequently, this study implicates CD1a-reactive cells as the primary responders to venom allergy, which considerably regulate the downstream immune response.

Targeting TSLP With shRNA Alleviates Airway Inflammation and Decreases Epithelial CCL17 in a Murine Model of Asthma

Airway epithelium defends the invasion from microorganisms and regulates immune responses in allergic asthma. Thymic stromal lymphopoietin (TSLP) from inflamed epithelium promotes maturation of dendritic cells (DCs) to prime Th2 responses via CCL17, which induces chemotaxis of CD4⁺ T cells to mediate inflammation. However, few studies have investigated the regulation of epithelial CCL17. In this study, we used shRNA against TSLP to clarify the role of TSLP in the airway inflammation and whether TSLP affects the airway inflammation via epithelial CCL17. Specific shTSLP was delivered by lentivirus and selected by the knockdown efficiency. Allergic mice were intratracheally pretreated with the lentivirus and followed by intranasal ovalbumin (OVA) challenges. The sera antibody levels, airway inflammation, airway hyper-responsiveness (AHR), cytokine levels in bronchoalveolar lavage fluids, and CCL17 expressions in lungs were determined. In vivo, TSLP attenuation reduced the AHR, decreased the airway inflammation, inhibited the maturations of DCs, and suppressed the migration of T cells. Furthermore, the expression of CCL17 was particularly decreased in bronchial epithelium. In vitro, CCL17 induction was regulated by TSLP. In conclusion, TSLP might coordinate airway inflammation partially via CCL17-mediated responses and this study provides the vital utility of TSLP to develop the therapeutic approach in allergic airway inflammation.

Prolonged allergen exposure is associated with increased thymic stromal lymphopoietin expression and Th2-skewing in mouse models of chronic rhinosinusitis

OBJECTIVES/HYPOTHESIS

Chronic rhinosinusitis (CRS) is characterized by a dysfunctional host-environment interaction at the nasal mucosa. Contributions of host susceptibility factors such as atopy and aspirin sensitivity to CRS pathophysiology are well established. However, clinical studies on the effects of environmental factors are limited. This study investigates the histological and immunological effects of allergen exposure duration in animal models.

STUDY DESIGN

Animal study.

METHODS

A murine model for CRS with nasal polypoid lesions was induced by instilling ovalbumin/staphylococcal enterotoxin B (SEB) into murine nasal cavities for 12 (short term) or 24 weeks (long term). Histopathological changes were observed. Interleukin (IL)-4, IL-17A, IL-10, and interferon (INF)-γ levels from nasal lavage fluid were measured using enzyme-linked immunosorbent assay. Gene expressions of IL-25, thymic stromal lymphopoietin (TSLP), IL-4, IL-5, INF-γ, C-C motif chemokine ligand (CCL)-11, CCL-24, C-X-C motif chemokine ligand (CXCL)-1, CXCL-2, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, matrix metallopeptidase (MMP)-7, and tissue inhibitor of metalloproteinase (TIMP)-3 were analyzed from the nasal mucosa.

RESULTS

Long-term CRS models exhibited increased polypoid lesions, edematous mucosal thickness, and eosinophil infiltration compared with short-term models and showed a higher IL-10 level but lower IFN-γ and IL-17A protein levels. Moreover, CCL-24 and MMP-7 gene expressions increased whereas TIMP-3 expression decreased in long-term models compared to controls and short-term models. IL-25 and TSLP expressions were upregulated at mRNA and protein levels in short-term and long-term CRS models, respectively. Furthermore, TSLP mRNA expression was positively associated with IL-5 (r = 0.8754) and inversely correlated to IFN-γ (r = -0.7212) in CRS models.

CONCLUSIONS

Prolonged allergen exposure in ovalbumin/SEB-induced CRS models maintains Th2 inflammation and reduces Th1 inflammation, which was associated with upregulation of TSLP.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E265-E272, 2016.

Adenosine influences myeloid cells to inhibit aeroallergen sensitization

Agonists of adenosine A2A receptors (A2ARs) suppress the activation of most immune cells and reduce acute inflammatory responses. Asthma is characterized by sensitization in response to initial allergen exposure and by airway hyperreactivity in response to allergen rechallenge. We sought to determine if A2AR activation with CGS-21680 (CGS) is more effective when CGS is administered during sensitization or rechallenge. C57BL/6 wild-type mice and Adora2a(f/f)LysMCre(+/-) mice, which lack A2ARs on myeloid cells, were sensitized with intranasal ovalbumin (OVA) and LPS. Airway sensitization was characterized by a rapid increase in numbers of IL-6(+) and IL-12(+) macrophages and dendritic cells in lungs. A2AR activation with CGS (0.1 μg·kg(-1)·min(-1) sc) only during sensitization reduced numbers of IL-6(+) and IL-12(+) myeloid cells in the lungs and reversed the effects of OVA rechallenge to increase airway hyperresponsiveness to methacholine. CGS treatment during sensitization also reduced the expansion of lung T helper (Th1 and Th17) cells and increased expansion of regulatory T cells in response to OVA rechallenge. Most of the effects of CGS administered during sensitization were eliminated by myeloid-selective A2AR deletion. Administration of CGS only during OVA rechallenge failed to reduce airway hyperresponsiveness. We conclude that myeloid cells are key targets of adenosine during sensitization and indirectly modify T cell polarization. The results suggest that a clinically useful strategy might be to use A2AR agonists to inhibit sensitization to new aeroallergens. We speculate that adenosine production by macrophages engulfing bacteria contributes to the curious suppression of sensitization in response to early-life infections.

Preferential Secretion of Thymic Stromal Lymphopoietin (TSLP) by Terminally Differentiated Esophageal Epithelial Cells: Relevance to Eosinophilic Esophagitis (EoE)

Eosinophilic esophagitis (EoE) is a chronic Th2 and food antigen-mediated disease characterized by esophageal eosinophilic infiltration. Thymic stromal lymphopoetin (TSLP), an epithelial derived cytokine which bridges innate and Th2-type adaptive immune responses in other allergic conditions, is overexpressed in esophageal biopsies of EoE subjects. However, the triggers of TSLP expression in the esophageal epithelium are unknown. The objective of the current study was to characterize TSLP expression in human esophageal epithelium in EoE in vivo and to determine the role of food antigens upon epithelial TSLP expression in vitro. Using immunohistochemistry (IHC), we localized TSLP in esophageal biopsies of active EoE (≥15 eos/hpf), inactive EoE (<15 eos/hpf) and non-EoE control subjects, and found that TSLP expression was restricted to the differentiated suprabasal layer of the epithelium in actively inflamed EoE biopsies. Consistent with these results in vivo, inducible TSLP protein secretion was higher in CaCl₂ differentiated telomerase-immortalized esophageal epithelial cells (EPC2-hTERT) compared to undifferentiated cells of the basal phenotype, following stimulation with the TLR3 ligand poly(I:C). To determine whether food antigens could directly induce epithelial TSLP secretion, differentiated and undifferentiated primary esophageal epithelial cells from EoE and non-EoE subjects were challenged with food antigens clinically relevant to EoE: Chicken egg ovalbumin (OVA), wheat, and milk proteins beta-lactoglobulin (blg) and beta-casein. Food antigens failed to induce TSLP secretion by undifferentiated cells; in contrast, only OVA induced TSLP secretion in differentiated epithelial cells from both EoE and control cell lines, an effect abolished by budesonide and NF-κb inhibition. Together, our study shows that specific food antigens can trigger innate immune mediated esophageal TSLP secretion, suggesting that esophageal epithelial cells at the barrier surface may play a significant role in the pathogenesis of EoE by regulating TSLP expression.

Regulation of Th2 Cell Immunity by Dendritic Cells

Th2 cell immunity is required for host defense against helminths, but it is detrimental in allergic diseases in humans. Unlike Th1 cell and Th17 cell subsets, the mechanism by which dendritic cells modulate Th2 cell responses has been obscure, in part because of the inability of dendritic cells to provide IL-4, which is indispensable for Th2 cell lineage commitment. In this regard, immune cells other than dendritic cells, such as basophils and innate lymphoid cells, have been suggested as Th2 cell inducers. More recently, multiple independent researchers have shown that specialized subsets of dendritic cells mediate Th2 cell responses. This review will discuss the current understanding related to the regulation of Th2 cell responses by dendritic cells and other immune cells.

Contributions of nonhematopoietic cells and mediators to immune responses: implications for immunotoxicology

Immunotoxicology assessments have historically focused on the effects that xenobiotics exhibit directly on immune cells. These studies are invaluable as they identify immune cell targets and help characterize mechanisms and/or adverse outcome pathways of xenobiotics within the immune system. However, leukocytes can receive environmental cues by cell-cell contact or via released mediators from cells of organs outside of the immune system. These organs include, but are not limited to, the mucosal areas such as the lung and the gut, the liver, and the central nervous system. Homeostatic perturbation in these organs induced directly by toxicants can initiate and alter the outcome of local and systemic immunity. This review will highlight some of the identified nonimmune influences on immune homeostasis and provide summaries of how immunotoxic mechanisms of selected xenobiotics involve nonimmune cells or mediators. Thus, this review will identify data gaps and provide possible alternative mechanisms by which xenobiotics alter immune function that could be considered during immunotoxicology safety assessment.

Food allergy in mice is modulated through the thymic stromal lymphopoietin pathway

Background

Thymic stromal lymphopoietin (TSLP) is involved in the pathogenesis of allergic reactions in the skin and the lung. Nevertheless, data on the role of TSLP in food allergy are scarce. We explored the role of TSLP in a mouse model with oral sensitization and oral challenge eliciting food allergy.

Methods

TSLP receptor (TSLPR)−/− mice and wild type mice were orally sensitized to β-lactoglobulin in presence of cholera toxin (CT) or CT alone. The elicited immune response was characterized in vitro and the mice were subsequently challenged with the antigen. Lymphocytes from various locations in the gut were activated either by the antigen or by CT and assayed for cytokine secretion.

Results

Here we report that TSLPR−/− are less prone to generate food-induced reactions in conjunction with a decreased antigen-specific IgG1, but not IgE response. In addition, mesenteric lymphnode lymphocytes of TSLPR−/− mice were secreting lower quantities of IL-4, IL-5 and IL-10 after in vivo Ag activation, whereas higher numbers of IL-17 secreting cells were observed. Similarly, activation by the Th2-type adjuvant cholera toxin resulted in an increased frequency of IL-12 and IL-17 secreting lamina propria and mesenteric lymphocytes, together with increased production of IL-12 by activated dendritic cells in TSLPR−/− mice.

Conclusions

TSLP can be considered as an essential, but not exclusive, mediator for elicitation of food allergy in mice, as well as a potential target for future therapeutic interventions.

Long-Acting Beta Agonists Enhance Allergic Airway Disease

Asthma is one of the most common of medical illnesses and is treated in part by drugs that activate the beta-2-adrenoceptor (β₂-AR) to dilate obstructed airways. Such drugs include long acting beta agonists (LABAs) that are paradoxically linked to excess asthma-related mortality. Here we show that LABAs such as salmeterol and structurally related β₂-AR drugs such as formoterol and carvedilol, but not short-acting agonists (SABAs) such as albuterol, promote exaggerated asthma-like allergic airway disease and enhanced airway constriction in mice. We demonstrate that salmeterol aberrantly promotes activation of the allergic disease-related transcription factor signal transducer and activator of transcription 6 (STAT6) in multiple mouse and human cells. A novel inhibitor of STAT6, PM-242H, inhibited initiation of allergic disease induced by airway fungal challenge, reversed established allergic airway disease in mice, and blocked salmeterol-dependent enhanced allergic airway disease. Thus, structurally related β₂-AR ligands aberrantly activate STAT6 and promote allergic airway disease. This untoward pharmacological property likely explains adverse outcomes observed with LABAs, which may be overcome by agents that antagonize STAT6.

Allergens, sources, particles, and molecules: Why do we make IgE responses?

Allergens are foreign proteins or glycoproteins that are the target of IgE antibody responses in humans. The relationship between subsequent exposure and the allergic symptoms is often or usually obvious; however, there is increasing evidence that in asthma, atopic dermatitis and some forms of food allergy the induction of symptoms is delayed or chronic. The primary exposure to inhaled allergens is to the particles, which are capable of carrying allergens in the air. Thus, the response reflects not only the properties of the proteins, but also the biological properties of the other constituents of the particle. This is best understood in relation to the mite fecal particles in which the contents include many different immunologically active substances. Allergic disease first became a major problem over 100 years ago, and for many years sensitization to pollens was the dominant form of these diseases. The rise in pediatric asthma correlates best with the move of children indoors, which started in 1960 and was primarily driven by indoor entertainment for children. While the causes of the increase are not simple they include both a major increase in sensitization to indoor allergens and the complex consequences of inactivity. Most recently, there has also been an increase in food allergy. Understanding this has required a reappraisal of the importance of the skin as a route for sensitization. Overall, understanding allergic diseases requires knowing about the sources, the particles and the routes of exposure as well as the properties of the individual allergens.

Murine allergic rhinitis and nasal Th2 activation are mediated via TSLP- and IL-33-signaling pathways

Thymic stromal lymphopoietin (TSLP) and IL-33 are epithelium-derived proallergic cytokines that contribute to allergic diseases. Although the involvement of TSLP in allergic rhinitis (AR) is suggested, the exact role of TSLP in AR is poorly understood. Furthermore, the relative contribution of TSLP and IL-33 in nasal allergic responses has not been described. In this study, we examined the roles of TSLP and IL-33 in AR by analyzing acute and chronic AR models. Acute AR mice were intraperitoneally immunized with ragweed, then intranasally challenged with ragweed pollen for four consecutive days. Chronic AR mice were nasally administrated ragweed pollen on consecutive days for 3 weeks. In both models, TSLP receptor (TSLPR)-deficient mice showed defective sneezing responses and reduced serum ragweed-specific IgE levels compared with wild-type (WT) mice. Analyses of bone-marrow chimeric mice demonstrated that hematopoietic cells were responsible for defective sneezing in TSLPR-deficient mice. In addition, FcεRI(+)-cell-specific TSLPR-deficient mice showed partial but significant reduction in sneezing responses. Of note, Th2 activation and nasal eosinophilia were comparable between WT and TSLPR-deficient mice. ST2- and IL-33-deficient mice showed defective Th2 activation and nasal eosinophilia to acute, but not chronic, ragweed exposure. TSLPR and ST2 double-deficient mice showed defective Th2 activation and nasal eosinophilia even after chronic ragweed exposure. These results demonstrate that TSLPR signaling is critical for the early phase response of AR by controlling the IgE-mast-cell/basophil pathway. The IL-33/ST2 pathway is central to nasal Th2 activation during acute allergen exposure, but both TSLPR and ST2 contribute to Th2 responses in chronically allergen-exposed mice.

Immunobiology of the critical asthma syndrome

It is now recognized that asthma incorporates a broad spectrum of syndromes with varying clinical manifestations. Future improvements in asthma treatment will require a clear characterization of these asthma phenotypes and the cellular mechanisms underlying these clinical manifestations. Herein, we will describe the current knowledge of asthma biology. This will include a review of the early pioneers in asthma and allergy, how this work led to our understanding of TH1 and TH2 cytokines, and the development of the "hygiene hypothesis." We will discuss the utility and limitations of the TH1-TH2 model of asthma in animal and human studies, and how this knowledge addresses controversies surrounding the hygiene hypothesis and other competing models. We will discuss novel therapies that have been developed based on mechanistic understanding of asthma pathobiology, including successes and shortcomings of these therapies. We will review the early work that led to the recognition of "asthma phenotypes." This will include the early discovery of various inflammatory subtypes in asthma and how these inflammatory subtypes correlate with response to therapy. Finally, we will describe recent discoveries in asthma biology that will include the role of the airway epithelium in asthma pathogenesis, novel cytokines important in asthma that may serve as novel therapeutic targets, and the identification of newly described innate immune cells and their role in asthma. Improved understanding of the complex biology underpinning the various asthma phenotypes is critical for our ability to optimize treatment for all patients that suffer from asthma and critical asthma syndromes.

The messenger between worlds: the regulation of innate and adaptive type-2 immunity by innate lymphoid cells

Although type-2 immune responses evolved primarily to defend against extracellular helminths, in part through the co-opting of tissue repair and remodeling mechanisms, they are often inappropriately directed towards relatively innocuous allergens resulting in conditions including asthma, allergic rhinitis, food allergy, and atopic dermatitis. The recent discovery of group 2 innate lymphoid cells (ILC2) has increased our understanding of the initiation of these responses and the roles played by CD4(+) T helper (Th) 2 cells in their modulation. This review focuses on the important messenger role of ILC2 in translating epithelial-derived alarmins into downstream adaptive type-2 responses via dendritic cells and T cells, with special emphasis on their roles in allergic disease.

Blockage of thymic stromal lymphopoietin signaling improves acute lung injury in mice by regulating pulmonary dendritic cells

OBJECTIVES

To investigate the effects of blockage of thymic stromal lymphopoietin (TSLP) signaling by TSLP receptor (TSLPR)-immunoglobulin (Ig) on acute lung injury (ALI) induced by lipopolysaccharide (LPS).

METHODS

C57BL/6 mice received TSLPR-Ig or controlled-Ig before being induced ALI. Lung wet/dry (W/D) weight ratio was recorded. Neutrophil number and albumin concentration of bronchoalveolar lavages fluids (BALF) were determined. Besides, bone marrow dendritic cells (BMDCs) were separated and cultured with medium, TSLP, TSLP plus TSLPR-Ig or TSLP plus controlled-Ig. Protein expression levels of TSLP in lung tissues, phosphorylation extracellular regulated protein kinases (pERK) 1/2, p38, and signal transducers and activators of transcription (STAT) 3 in BMDCs were analyzed using Western blotting. Expression of CD40, CD80 and CD86 on pulmonary DCs and BMDCs was determined using flow cytometry (FCM).

RESULTS

The W/D ratio, neutrophil number and albumin concentration were significantly decreased in the TSLPR-Ig group compared with the controlled-Ig and model group. Moreover, there was a noticeable decrease in CD40, CD80 or CD86 expression by TSLPR-Ig on both pulmonary DCs and BMDCs. The protein levels of TSLP, pERK1 and STAT3 were significantly decreased by TSLPR-Ig. However, no significant differences were found in p38 and pERK2.

CONCLUSION

These results suggest that TSLP may be involved in ALI, and blockage of TSLP signaling using TSLPR-Ig improves ALI at least in part by regulation of DCs functions. The underling downstream signaling mediated by TSLP might be associated with activating the ERK1 and STAT3 signaling pathway.

Triclosan Induces Thymic Stromal Lymphopoietin in Skin Promoting Th2 Allergic Responses

Triclosan is an antimicrobial chemical incorporated into many personal, medical and household products. Approximately, 75% of the U.S. population has detectable levels of triclosan in their urine, and although it is not typically considered a contact sensitizer, recent studies have begun to link triclosan exposure with augmented allergic disease. We examined the effects of dermal triclosan exposure on the skin and lymph nodes of mice and in a human skin model to identify mechanisms for augmenting allergic responses. Triclosan (0%-3%) was applied topically at 24-h intervals to the ear pinnae of OVA-sensitized BALB/c mice. Skin and draining lymph nodes were evaluated for cellular responses and cytokine expression over time. The effects of triclosan (0%-0.75%) on cytokine expression in a human skin tissue model were also examined. Exposure to triclosan increased the expression of TSLP, IL-1β, and TNF-α in the skin with concomitant decreases in IL-25, IL-33, and IL-1α. Similar changes in TSLP, IL1B, and IL33 expression occurred in human skin. Topical application of triclosan also increased draining lymph node cellularity consisting of activated CD86(+)GL-7(+) B cells, CD80(+)CD86(+) dendritic cells, GATA-3(+)OX-40(+)IL-4(+)IL-13(+) Th2 cells and IL-17 A(+) CD4 T cells. In vivo antibody blockade of TSLP reduced skin irritation, IL-1β expression, lymph node cellularity, and Th2 responses augmented by triclosan. Repeated dermal exposure to triclosan induces TSLP expression in skin tissue as a potential mechanism for augmenting allergic responses.

Elevated IL-3 and IL-12p40 levels in the lower airway of infants with RSV-induced bronchiolitis correlate with recurrent wheezing

Respiratory Syncytial Virus (RSV) is the first cause of hospitalization due to bronchiolitis in infants. RSV bronchiolitis has been linked to asthma and recurrent wheezing, however the mechanisms behind this association have not been elucidated. Here, we evaluated the cytokine and chemokine profiles in the airways in infants with RSV bronchiolitis. Nasopharyngeal Aspirates (NPA) and Bronchoalveolar Lavage Fluids (BALF) from infants hospitalized due to RSV bronchiolitis and healthy controls were analyzed for cytokine and chemokine production. We observed elevated levels of Th2 cytokines (IL-3, IL-4, IL-10 and IL-13), pro-inflammatory cytokines and chemokines (IL-1β, IL-6, TNF-β, MCP-1/CCL2, MIP-1α/CCL3 and IL-8/CXCL8) in BALF from infants with RSV bronchiolitis, as compared to controls. We found a direct correlation of IL-3 and IL-12p40 levels with the development of recurrent wheezing later in life. These results suggest that IL-3 and IL-12p40 could be considered as molecular predictors for recurrent wheezing due to RSV infection.

Correlation of TSLP, IL-33, and CD4 + CD25 + FOXP3 + T regulatory (Treg) in pediatric asthma

OBJECTIVE

Newly discovered cytokines TSLP and IL33 are being studied as important indicators of Th2 inflammation and their effect on Treg cells is likely to modulate immune response. We attempted to study TSLP and IL-33 and then correlated with Tregs in order to find possible biomarker in these patients.

METHODS

Sixty-five children (37 with asthma only and 28 with asthma and rhinitis) aged 6.4 ± 3.2 years (patient group) and 15 healthy children aged 8.0 ± 2.6 years (control group) were recruited in this study. In vitro analysis of TSLP and IL-33 was done in serum samples of 65 newly diagnosed children for allergic asthma and 15 healthy children using the sandwich ELISA method. The expression of Treg cells (CD4 + CD25 + FOXP3+) was analyzed by flow cytometry.

RESULTS

The mean TSLP in the patient group (592 ± 68 pg/ml) was significantly higher than controls (215 ± 45 pg/ml) (p < 0.05). Alternatively, the expression of FOXP3 + T reg cells was significantly lower in the patient group (52 ± 36) compared with the controls (95.9 ± 3.6) (p = 0.003). IL-33 was also significantly higher (4044 ± 413 pg/ml) in the patient group compared with the controls (3282 ± 331.5 pg/ml) (p = 0.0001). The expression of Treg cells was negatively correlated with the TSLP (r = -0.23, p = 0.07). Asthma control test (ACT) was also negatively correlated with TSLP in the patient group (r = -0.14, p > 0.05).

CONCLUSION

Children with asthma show elevated serum levels of TSLP, which correlated negatively with asthma control test and Treg cells. TSLP may be used as a biomarker for inflammation in pediatric asthma patients.

Deciphering Asthma Biomarkers with Protein Profiling Technology

Asthma is a chronic inflammatory disease of the airways, resulting in bronchial hyperresponsiveness with every allergen exposure. It is now clear that asthma is not a single disease, but rather a multifaceted syndrome that results from a variety of biologic mechanisms. Asthma is further problematic given that the disease consists of many variants, each with its own etiologic and pathophysiologic factors, including different cellular responses and inflammatory phenotypes. These facets make the rapid and accurate diagnosis (not to mention treatments) of asthma extremely difficult. Protein biomarkers can serve as powerful detection tools in both clinical and basic research applications. Recent endeavors from biomedical researchers have developed technical platforms, such as cytokine antibody arrays, that have been employed and used to further the global analysis of asthma biomarker studies. In this review, we discuss potential asthma biomarkers involved in the pathophysiologic process and eventual pathogenesis of asthma, how these biomarkers are being utilized, and how further testing methods might help improve the diagnosis and treatment strain that current asthma patients suffer.

Rhinovirus-Induced Airway Disease: A Model to Understand the Antiviral and Th2 Epithelial Immune Dysregulation in Childhood Asthma

Rhinovirus (RV) infections account for most asthma exacerbations among children and adults, yet the fundamental mechanism responsible for why asthmatics are more susceptible to RV than otherwise healthy individuals remains largely unknown. Nonetheless, the use of models to understand the mechanisms of RV-induced airway disease in asthma has dramatically expanded our knowledge about the cellular and molecular pathogenesis of the disease. For instance, ground-breaking studies have recently established that the susceptibility to RV in asthmatic subjects is associated with a dysfunctional airway epithelial inflammatory response generated after innate recognition of viral-related molecules, such as double-stranded RNA. This review summarizes the novel cardinal features of the asthmatic condition identified in the past few years through translational and experimental RV-based approaches. Specifically, we discuss the evidence demonstrating the presence of an abnormal innate antiviral immunity (airway epithelial secretion of types I and III interferons), exaggerated production of the master Th2 molecule thymic stromal lymphopoietin, and altered antimicrobial host defense in the airways of asthmatic individuals with acute RV infection.

IL-25 and IL-33 Contribute to Development of Eosinophilic Airway Inflammation in Epicutaneously Antigen-Sensitized Mice

BACKGROUND

IL-25, IL-33 and TSLP are produced predominantly by epithelial cells and are known to induce Th2-type cytokines. Th2-type cytokines are involved not only in host defense against nematodes, but also in the development of Th2-type allergic diseases. TSLP was reported to be crucial for development of allergic airway inflammation in mice after inhalation of allergens to which they had been sensitized epicutaneously (EC) beforehand. However, the roles of IL-25 and IL-33 in the setting remain unclear.

METHODS

Mice deficient in IL-25 and IL-33 were sensitized EC with ovalbumin (OVA) and then challenged intranasally with OVA. Airway inflammation, the number of inflammatory cells in bronchoalveolar lavage fluids (BALFs) and airway hyperresponsiveness (AHR) in the mice were determined, respectively, by histological analysis, with a hemocytometer, and by using plethysmograph chambers with a ventilator. Expression of mRNA in the skin and lungs was determined by quantitative PCR, while the BALF levels of myeloperoxidase (MPO) and eosinophil peroxidase (EPO) and the serum levels of IgE were determined by ELISA.

RESULTS

Normal OVA-specific Th2- and Th17-cell responses of lymph nodes and spleens were observed in IL-25-deficient (IL-25-/-) and IL-33-/- mice after EC sensitization with OVA. Nevertheless, the number of eosinophils, but not neutrophils, in the BALFs, and the levels of Th2 cytokines, but not Th17 cytokines, in the lungs were significantly decreased in the IL-25-/- and IL-33-/- mice pre-sensitized EC with OVA, followed by inhalation of OVA, whereas their levels of AHR and OVA-specific serum IgE were normal.

CONCLUSIONS

Both IL-25 and IL-33 are critical for induction of Th2-type cytokine-mediated allergic airway eosinophilia, but not Th17-type cytokine-mediated airway neutrophilia, at the local sites of lungs in the challenge phase of mice sensitized EC with OVA. They do not affect OVA-specific T-cell induction in the sensitization phase.

The importance of TSLP in allergic disease and its role as a potential therapeutic target

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine similar to IL- 7, whose gene is located on chromosome 5q22.1 and it exerts its biological function through the TSLP-Receptor (TSLP-R). TSLP is expressed primarily by epithelial cells at barrier surfaces such as the skin, gut and lung in response to danger signals. Since it was cloned in 1994, there has been accumulating evidence that TSLP is crucial for the maturation of antigen presenting cells and hematopoietic cells. TSLP genetic variants and its dysregulated expression have been linked to atopic diseases such as atopic dermatitis, asthma, allergic rhinitis and eosinophilic esophagitis.

The Additive Inflammatory In Vivo and In Vitro Effects of IL-7 and TSLP in Arthritis Underscore the Therapeutic Rationale for Dual Blockade

INTRODUCTION

The cytokines interleukin (IL)-7 and thymic stromal lymphopoietin (TSLP) signal through the IL-7R subunit and play proinflammatory roles in experimental arthritis and rheumatoid arthritis (RA). We evaluated the effect of inhibition of IL-7R- and TSLPR-signalling as well as simultaneous inhibition of IL-7R- and TSLPR-signalling in murine experimental arthritis. In addition, the effects of IL-7 and TSLP in human RA dendritic cell (DC)/T-cell co-cultures were studied.

METHODS

Arthritis was induced with proteoglycan in wildtype mice (WT) and in mice deficient for the TSLP receptor subunit (TSLPR-/-). Both mice genotypes were treated with anti-IL-7R or phosphate buffered saline. Arthritis severity was assessed and local and circulating cytokines were measured. Autologous CD1c-positive DCs and CD4 T-cells were isolated from peripheral blood of RA patients and were co-cultured in the presence of IL-7, TSLP or both and proliferation and cytokine production were assessed.

RESULTS

Arthritis severity and immunopathology were decreased in WT mice treated with anti-IL-7R, in TSLPR-/- mice, and the most robustly in TSLPR-/- mice treated with anti-IL-7R. This was associated with strongly decreased levels of IL-17, IL-6 and CD40L. In human DC/T-cell co-cultures, TSLP and IL-7 additively increased T-cell proliferation and production of Th17-associated cytokines, chemokines and tissue destruction factors.

CONCLUSION

TSLP and IL-7 have an additive effect on the production of Th17-cytokines in a human in vitro model, and enhance arthritis in mice linked with enhanced inflammation and immunopathology. As both cytokines signal via the IL-7R, these data urge for IL-7R-targeting to prevent the activity of both cytokines in RA.

Rhinovirus infection interferes with induction of tolerance to aeroantigens through OX40 ligand, thymic stromal lymphopoietin, and IL-33

BACKGROUND

Rhinovirus infection at an early age has been associated with development of asthma, but how rhinovirus influences the immune response is not clear.

OBJECTIVE

Tolerance to inhaled antigen is mediated through induction of regulatory T (Treg) cells, and we examined whether rhinovirus infection of the respiratory tract can block airway tolerance by modulating Treg cells.

METHODS

The immune response to intranasal ovalbumin in mice was assessed with concomitant infection with RV1B, and the factors induced in vivo were compared with those made by human lung epithelial cells infected in vitro with RV16.

RESULTS

RV1B infection of mice abrogated tolerance induced by inhalation of soluble ovalbumin, suppressing the normal generation of forkhead box protein 3-positive Treg cells while promoting TH2 cells. Furthermore, RV1B infection led to susceptibility to asthmatic lung disease when mice subsequently re-encountered aeroantigen. RV1B promoted early in vivo expression of the TNF family protein OX40 ligand on lung dendritic cells that was dependent on the innate cytokine thymic stromal lymphopoietin (TSLP) and also induced another innate cytokine, IL-33. Inhibiting each of these pathways allowed the natural development of Treg cells while minimizing TH2 differentiation and restored tolerance in the face of RV1B infection. In accordance, RV16 infection of human lung epithelial cells upregulated TSLP and IL-33 expression.

CONCLUSIONS

These results suggest that infection of the respiratory epithelium with rhinovirus can antagonize tolerance to inhaled antigen through combined induction of TSLP, IL-33, and OX40 ligand and that this can lead to susceptibility to asthmatic lung inflammation.

Thymic stromal lymphopoietin deficiency attenuates experimental autoimmune encephalomyelitis

In the present study we examined the role of thymic stromal lymphopoietin (TSLP) in experimental autoimmune encephalomyelitis (EAE). Here, we report that TSLP knock-out (KO) mice display a delayed onset of disease and an attenuated form of EAE. This delayed onset was accompanied by a reduced number of encephalitogenic T helper type 1 (Th1) cells in the central nervous system (CNS) of TSLP KO mice. In addition, CD4(+) and CD8(+) T cells from CNS of TSLP KO mice show a reduced activation status in comparison to wild-type mice. It is noteworthy that we could also show that lymph node cells from TSLP KO mice expanded less efficiently and that interleukin (IL)-6-, interferon (IFN)-γ and tumour necrosis factor (TNF)-α levels were reduced. Furthermore, CD3(+) T cells isolated in the preclinical phase from myelin oligodendrocyte glycoprotein peptide 35-55 (MOG(35-55))-immunized TSLP KO mice showed a reduced response after secondary exposure to MOG(35-55), indicating that differentiation of naive T cells into MOG(35-55)-specific effector and memory T cells was impaired in KO mice. The addition of recombinant TSLP enhanced T cell proliferation during MOG(35-55) restimulation, showing that T cells also respond directly to TSLP. In summary, these data demonstrate that expression of, and immune activation by, TSLP contributes significantly to the immunopathology of EAE.

Lung-derived SSEA-1(+) stem/progenitor cells inhibit allergic airway inflammation in mice

BACKGROUND

Asthma is characterized by chronic airway inflammation and airway hyperresponsiveness (AHR). Little is known about the role of pulmonary stem/progenitor cells (PSCs) in allergic airway inflammation.

METHODS

To identify and investigate the role of PSCs in the bronchial epithelium of neonatal mice, we developed an enzyme-based digestion method to obtain single-cell suspension from lung tissues. Characterization of PSCs was performed using flow cytometry, real-time PCR, immunofluorescence staining, confocal microscopy, and scanning electron microscopy. The effects of SSEA-1(+) (stage-specific embryonic antigen-1) PSCs was studied in an in vivo model of ovalbumin-induced allergic inflammation and an in vitro model of cell-based regulation using flow cytometry, real-time PCR, and immune-blotting.

RESULTS

Single-cell suspensions derived from neonatal lung tissue included populations that expressed either SSEA-1(+) or Sca-1(+) (stem cell antigen-1). The SSEA-1(+) PSCs were highly prevalent in neonatal mice, and they were rare in adult mice. Enriched neonatal SSEA-1(+) PSCs had the ability of self-renewal and differentiated into pneumocytes and tracheal epithelial cells. SSEA-1(+) PSCs reduced AHR and airway damage in asthmatic mice by decreasing eosinophil infiltration, inhibiting chemokines/cytokines production, and preserving the level of CCSP.

CONCLUSIONS

Here, we demonstrated that neonatal SSEA-1(+) PSCs play an immunomodulatory role in the progression of asthma by reducing lung damage and inhibiting inflammatory responses. Further understanding the molecular mechanisms of neonatal SSEA-1(+) PSCs might shed light on exploring the novel therapeutic approaches for allergic airway inflammation.