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BACKGROUND: Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine important in initiation of allergic inflammation. Single nucleotide polymorphisms (SNPs) in TSLP are associated with asthma, yet studies have shown inconsistent associations between circulating TSLP and asthma. Studies that integrate the combined effects of TSLP genotype, TSLP mRNA, circulating TSLP levels, and asthma outcome are lacking. OBJECTIVE: To recruit a novel cohort based on asthma-relevant TSLP SNPs and determine their impact on TSLP mRNA expression and TSLP circulating protein levels, and their individual and combined effects on asthma. METHODS: We developed an algorithm to prioritize TSLP SNPs and recruited 51 carriers and non-carriers based on TSLP genotypes. We quantified TSLP mRNA in nasal epithelial cells and circulating TSLP levels in plasma. We determined associations of defined TSLP risk genotypes and/or TSLP mRNA and protein levels with asthma. RESULTS: TSLP mRNA expression, but not circulating TSLP, was significantly increased in asthmatics compared to non-asthmatics (P=0.007; OR=1.44). Notably, 90% of children with the defined TSLP risk genotypes and high nasal TSLP mRNA expression (top tertile) had asthma compared to 40% of subjects without risk genotypes and with low TSLP expression (bottom tertile) (P=0.024). No association between circulating TSLP and asthma was observed. CONCLUSION: Collectively, these data suggest childhood asthma is modified by the combined effects of TSLP genotype and TSLP expression in the nasal epithelium. The increased asthma risk likely manifests when genetic variation enables eQTL in the TSLP locus to elevate TSLP. It is important to consider both biomarkers when factoring asthma risk. CLINICAL IMPLICATIONS: TSLP genotype and nasal mRNA expression may be useful biomarkers to aid asthma prediction and/or identify individuals who would benefit from therapy targeting this pathway.

Aspirin exacerbated respiratory disease (AERD) is a complex inflammatory disorder that is not generally viewed as a disease involving the adaptive immune system but instead one largely driven by the innate immune system. This article focuses on the cellular dysregulation involving four central cell types: eosinophils, basophils, mast cells (MC), and innate lymphoid type 2 (ILC2) cells. AERD can be envisioned as involving a self-perpetuating vicious circle in which mediators produced by a differentiated activated epithelial layer, such as interleukin (IL)-25, IL-33, and thymic stromal lymphopoietin (TSLP) engage and activate each of these innate immune cells. The activation of these innate immune cells with their production of additional cytokine/chemokine and lipid mediators leads to further recruitment and activation of these innate immune cells. More importantly, numerous mediators produced by these innate immune cells provoke the epithelium to induce further inflammation. This self-perpetuating cycle of inflammation partially explains both current interventions suggested to ameliorate AERD (e.g., aspirin desensitization, leukotriene modifiers, anti-IL-5/IL-5 receptor, anti-IL-4 receptor, anti-IgE) and invites exploration of novel targets as specific therapies for this condition (prostaglandin D(2) antagonists or cytokine antagonists (IL-25, IL-33, TSLP). Several of these interventions currently show promise in small retrospective analyses but now require definite clinical trials.

IL-25, also known as IL-17E, is a unique cytokine of the IL-17 family. Indeed, IL-25 exclusively was shown to strongly induce expression of the cytokines associated with type 2 immunity. Although produced by several types of immune cells, such as T cells, dendritic cells, or group 2 innate lymphoid cells, a vast amount of IL-25 derives from epithelial cells. The functions of IL-25 have been actively studied in the context of physiology and pathology of various organs including skin, airways and lungs, gastrointestinal tract, and thymus. Accumulating evidence suggests that IL-25 is a "barrier surface" cytokine whose expression depends on extrinsic environmental factors and when upregulated may lead to inflammatory disorders such as atopic dermatitis, psoriasis, or asthma. This review summarizes the progress of the recent years regarding the effects of IL-25 on the regulation of immune response and the balance between its homeostatic and pathogenic role in various epithelia. We revisit IL-25's general and tissue-specific mechanisms of action, mediated signaling pathways, and transcription factors activated in immune and resident cells. Finally, we discuss perspectives of the IL-25-based therapies for inflammatory disorders and compare them with the mainstream ones that target IL-17A.

Taking a novel approach, this narrative review collates knowledge about nasal polyposis and the biological functions of IgE in several diseases (allergic rhinitis, allergic asthma, nonsteroidal anti-inflammatory drugs-exacerbated respiratory disease, and chronic spontaneous urticaria) to consider which IgE-mediated mechanisms are relevant to nasal polyposis pathology. A type 2 eosinophil-dominated inflammatory signature is typical in nasal polyp tissue of European patients with nasal polyposis, with a shift toward this endotype observed in Asian populations in recent years. Elevated polyclonal IgE is present in the nasal tissue of patients with and without allergy. It is derived from many different B-cell clones and, importantly, is functional (proinflammatory). Staphylococcus aureus enterotoxins are thought to act as superantigens, inducing production of polyclonal IgE via B-cell and T-cell activation, and triggering release of inflammatory mediators. In some patients, exposure to antigens/triggers leads to production of high levels of antigen-specific IgE, which mediates cross-linking of the high-affinity IgE receptor on various cells, causing release of inflammatory mediators. The efficacy of omalizumab confirms IgE as an important inflammatory mediator in nasal polyposis. By blocking IgE, omalizumab targets the T2 inflammation in nasal polyposis, reduces nasal polyp score and improves symptoms.

Background The selective reduction of memory TH2 cell responses could be key to affording tolerance and protection from the recurrence of damaging allergic pathology. Objective We asked whether TNF family costimulatory molecules cooperated to promote accumulation and reactivity of effector memory CD4 T cells to inhaled complex allergen, and whether their neutralization could promote airway tolerance to subsequent reexposure to allergen. Methods Mice were sensitized intraperitoneally or intranasally with house dust mite and challenged with intranasal allergen after memory had developed. We assessed whether single or combined blockade of OX40L/CD252 and CD30L/CD153 inhibited memory T cells from driving acute asthmatic lung inflammation and protected mice following exposure to allergen at a later time. Results OX40- or CD30-deficient animals showed strong or partial protection against allergic airway inflammation; however, neutralizing either molecule alone during the secondary response to allergen had little effect on the frequency of effector memory CD4 T cells formed and acute lung inflammation. In contrast, a significant reduction in eosinophilic inflammation was observed when OX40L and CD30L were simultaneously neutralized, with dual blockade inhibiting effector memory TH2 cell expansion in the lungs, whereas formation of peripherally induced regulatory T cells remained intact. Moreover, dual blockade during the secondary response resulted in a tolerogenic state such that mice did not develop a normal tertiary memory TH2 cell and lung inflammatory response when challenged weeks later with allergen. Conclusion Memory T-cell responses to complex allergens are controlled by several TNF costimulatory interactions, and their combination targeting might represent a strategy to reduce the severity of inflammatory reactions following reexposure to allergen.

Background Natural killer T (NKT) cells are unconventional T cells that bridge innate and adaptive immunity. NKT cells have been implicated in the development of atopic dermatitis (AD). Objective We aimed to investigate the role of NKT cells in AD development, especially in skin. Methods Global proteomic and transcriptomic analyses were performed by using skin and blood from human healthy–controls and patients with AD. Levels of CXCR4 and CXCL12 expression in skin NKT cells were analyzed in human AD and mouse AD models. By using parabiosis and intravital imaging, the role of skin CXCR4+ NKT cells was further evaluated in models of mice with AD by using CXCR4–conditionally deficient or CXCL12 transgenic mice. Results CXCR4 and its cognate ligand CXCL12 were significantly upregulated in the skin of humans with AD by global transcriptomic and proteomic analyses. CXCR4+ NKT cells were enriched in AD skin, and their levels were consistently elevated in our models of mice with AD. Allergen-induced NKT cells participate in cutaneous allergic inflammation. Similar to tissue-resident memory T cells, the predominant skin NKT cells were CXCR4+ and CD69+. Skin-resident NKT cells uniquely expressed CXCR4, unlike NKT cells in the liver, spleen, and lymph nodes. Skin fibroblasts were the main source of CXCL12. CXCR4+ NKT cells preferentially trafficked to CXCL12-rich areas, forming an enriched CXCR4+ tissue-resident NKT cells/CXCL12+ cell cluster that developed in acute and chronic allergic inflammation in our models of mice with AD. Conclusions CXCR4+ tissue-resident NKT cells may form a niche that contributes to AD, in which CXCL12 is highly expressed.

Background Arginine methylation is a posttranslational modification mediated by protein arginine methyltransferases (PRMTs). Although previous studies have shown that PRMT1 contributes to the severity of allergic airway inflammation or asthma, the underlying mechanism is poorly understood. Objective This study aimed to explore the role of PRMT1 and its relevant mechanism in the development of allergic rhinitis (AR). Methods The expression levels of PRMTs and cytokines were determined by RT-PCR, and the localization of PRMT1 was determined by immunohistochemistry and confocal microscopy. The levels of house dust mite (HDM)-specific immunoglobulins in serum and of cytokines in nasal lavage fluids were determined by ELISA. PRMT1 inhibition was achieved by siRNA and treatment with the pan PRMT inhibitor arginine N-methyltransferase inhibitor-1. Results PRMT1 expression was significantly increased in the nasal mucosa of patients and mice with AR. The degree of eosinophilic infiltration in the nasal mucosa was reduced in PRMT1+/− AR mice compared with wild-type mice. PRMT1 haploinsufficiency reduced the levels of HDM-specific immunoglobulins in serum and those of TH2 (IL-4, IL-5, and IL-13) and epithelial (thymic stromal lymphopoietin [TSLP], IL-25, and IL-33) cytokines in the nasal lavage fluids of AR mice. In nasal epithelial cells, HDM and IL-4 cooperate to enhance PRMT1 expression through a mitogen-activated protein kinase–dependent pathway. In addition, PRMT1 was essential for the production of TSLP, IL-25, and IL-33 in response to HDM and IL-4. Arginine N-methyltransferase inhibitor-1 treatment alleviated AR in the mouse model. Conclusions PRMT1 plays an important role in AR development by regulating epithelial-derived cytokine production and might be a new therapeutic target for AR.

Background Cannabinoids modulate the activation of immune cells and physiological processes in the lungs. Group-2 innate lymphoid cells (ILC2)s are central players in type-2 asthma, but how cannabinoids modulate ILC2 activation remains to be elucidated Objective Our goal is to investigate the effects of cannabinoids on ILC2s and their role in asthma. Methods A combination of Cannabinoid receptor (CB)2 KO mice, CB2 antagonist and agonist were used in the mouse models of IL-33, IL-25 and Alternaria alternata ILC2-dependent airway inflammation, and RNA sequencing was performed to assess transcriptomic changes in ILC2s. Humanized mice were used to assess the role of CB2 signaling in human ILC2s. Results We here provide evidence that CB2 signaling in ILC2s is important for the development of ILC2-driven airway inflammation in both mice and human. We showed that both naive and activated murine pulmonary ILC2s express CB2. CB2 signaling did not affect ILC2 homeostasis at steady state, but strikingly stimulated ILC2 proliferation and function upon activation. As a result, ILC2s lacking CB2 induced lower lung inflammation, as we made similar observations using a CB2 antagonist. Conversely, CB2 agonism remarkably exacerbated ILC2-driven airway hyperreactivity and lung inflammation. Mechanistically, transcriptomic and protein analysis revealed that CB2 signaling induced CREB phosphorylation in ILC2s. Human ILC2s expressed CB2, as CB2 antagonism and agonism showed opposing effects on ILC2 effector function and development of airway hyperreactivity in humanized mice. Conclusion Collectively, our results define CB2 signaling in ILC2s as an important modulator of airway inflammation.

Itch is a common sensory experience that is prevalent in patients with inflammatory skin diseases, as well as in those with systemic and neuropathic conditions. In patients with these conditions, itch is often severe and significantly affects quality of life. Itch is encoded by 2 major neuronal pathways: histaminergic (in acute itch) and nonhistaminergic (in chronic itch). In the majority of cases, crosstalk existing between keratinocytes, the immune system, and nonhistaminergic sensory nerves is responsible for the pathophysiology of chronic itch. This review provides an overview of the current understanding of the molecular, neural, and immune mechanisms of itch: beginning in the skin, proceeding to the spinal cord, and eventually ascending to the brain, where itch is processed. A growing understanding of the mechanisms of chronic itch is expanding, as is our pipeline of more targeted topical and systemic therapies. Our therapeutic armamentarium for treating chronic itch has expanded in the last 5 years, with developments of topical and systemic treatments targeting the neural and immune systems.

Neuroimmune interaction has long been discussed in the pathogenesis of allergic airway diseases, such as allergic asthma. Mediators released during inflammation can alter the function of both sensory and parasympathetic neurons innervating the airways. Evidence has been provided that the inflammatory response can be altered by various mediators that are released by sensory and parasympathetic neurons and vice versa. Our aim is to demonstrate recent developments in the reciprocal neuroimmune interaction and to include, if available, data from in vivo and clinical studies.

Until recently, basophils had often been neglected in immunologic studies because of their minority status among immune cells or confused with tissue-resident mast cells because of some phenotypic similarities between them in spite of different anatomic localization. It is now appreciated that basophils and mast cells are distinct cell lineages and that basophils play important and nonredundant roles distinct from those played by mast cells. On the one hand, basophils contribute beneficially to protective immunity, particularly against parasitic infections. On the other hand, basophils are involved in the development of various disorders, including allergy and autoimmune disease. Basophils interact with other immune cells and nonhematopoietic cells through cell-to-cell contact or basophil-derived factors, such as cytokines and proteases, contributing to the regulation of immune and allergic responses. In this review article we highlight recent advances in our understanding of basophil pathophysiology in human subjects and animal models by consolidating research findings reported during the past 5 years. Further studies on basophils and their products will help identify suitable targets for novel therapeutics in allergy and effective vaccines against parasitic infection.

BACKGROUND: Eosinophilic esophagitis (EoE) is an esophageal inflammatory disease associated with atopic diseases. Thymic stromal lymphopoietin (TSLP) and calpain 14 (CAPN14) genetic variations contribute to EoE, but how this relates to atopy is unclear. OBJECTIVE: The purpose of this study was to explore the relationship between EoE, atopy, and genetic risk. METHODS: EoE-atopy enrichment was tested by using 700 patients with EoE and 801 community control subjects. Probing 372 single nucleotide polymorphisms (SNPs) in 63 atopy genes, we evaluated EoE associations using 412 nonatopic and 868 atopic disease control subjects. Interaction and stratified analyses of EoE-specific and atopy-related SNPs were performed. RESULTS: Atopic disease was enriched in patients with EoE (P < .0001). Comparing patients with EoE and nonatopic control subjects, EoE associated strongly with IL-4/kinesin family member 3A (IL4/KIF3A) (P = 2.8 × 10(−6); odds ratio [OR], 1.87), moderately with TSLP (P = 1.5 × 10(−4); OR, 1.43), and nominally with CAPN14 (P = .029; OR, 1.35). Comparing patients with EoE with atopic disease control subjects, EoE associated strongly with ST2 (P = 3.5 × 10(−6); OR, 1.77) and nominally with IL4/KIF3A (P = .019; OR, 1.25); TSLP’s association persisted (P = 4.7 × 10(−5); OR, 1.37), and CAPN14’s association strengthened (P = .0001; OR, 1.71). Notably, there was gene-gene interaction between TSLP and IL4 SNPs (P = .0074). Children with risk alleles for both genes were at higher risk for EoE (P = 2.0 × 10(−10); OR, 3.67). CONCLUSIONS: EoE genetic susceptibility is mediated by EoE-specific and general atopic disease loci, which can have synergistic effects. These results might aid in identifying potential therapeutics and predicting EoE susceptibility.

Background The type 2 cytokines IL-4 and IL-13 promote not only atopic dermatitis (AD) but also the resolution of inflammation. How type 2 cytokines participate in the resolution of AD is poorly known. Objective Our aim was to determine the mechanisms and cell types governing skin inflammation, barrier dysfunction, and resolution of inflammation in a model of AD. Methods Mice that exhibit expression of IL-4, IL-13, and MCPT8 or that could be depleted of basophils or eosinophils, be deficient in IL-4 or MHC class II molecules, or have basophils lacking macrophage colony-stimulating factor (M-CSF) were treated with calcipotriol (MC903) as an acute model of AD. Kinetics of the disease; keratinocyte differentiation; and leukocyte accumulation, phenotype, function, and cytokine production were measured by transepidermal water loss, histopathology, molecular biology, or unbiased analysis of spectral flow cytometry. Results In this model of AD, basophils were activated systemically and were the initial and main source of IL-4 in the skin. Basophils and IL-4 promoted epidermal hyperplasia and skin barrier dysfunction by acting on keratinocyte differentiation during inflammation. Basophils, IL-4, and basophil-derived M-CSF inhibited the accumulation of proinflammatory cells in the skin while promoting the expansion and function of proresolution M2-like macrophages and the expression of probarrier genes. Basophils kept their proresolution properties during AD resolution. Conclusion Basophils can display both beneficial and detrimental type 2 functions simultaneously during atopic inflammation.

Background Atopic dermatitis (AD) is a complex, chronic, inflammatory skin disease with a diverse clinical presentation. However, it is unclear whether this diversity exists at a biological level. Objective We sought to test the hypothesis that AD is heterogeneous at the biological level of individual inflammatory mediators. Methods Sera from 193 adult patients with moderate-to-severe AD (six area, six sign atopic dermatitis [SASSAD] score: geometric mean, 22.3 [95% CI, 21.3-23.3] and 39.1 [95% CI, 37.5-40.9], respectively) and 30 healthy control subjects without AD were analyzed for 147 serum mediators, total IgE levels, and 130 allergen-specific IgE levels. Population heterogeneity was assessed by using principal component analysis, followed by unsupervised k-means cluster analysis of the principal components. Results Patients with AD showed pronounced evidence of inflammation compared with healthy control subjects. Principal component analysis of data on sera from patients with AD revealed the presence of 4 potential clusters. Fifty-seven principal components described approximately 90% of the variance. Unsupervised k-means cluster analysis of the 57 largest principal components delivered 4 distinct clusters of patients with AD. Cluster 1 had high SASSAD scores and body surface areas with the highest levels of pulmonary and activation-regulated chemokine, tissue inhibitor of metalloproteinases 1, and soluble CD14. Cluster 2 had low SASSAD scores with the lowest levels of IFN-α, tissue inhibitor of metalloproteinases 1, and vascular endothelial growth factor. Cluster 3 had high SASSAD scores with the lowest levels of IFN-β, IL-1, and epithelial cytokines. Cluster 4 had low SASSAD scores but the highest levels of the inflammatory markers IL-1, IL-4, IL-13, and thymic stromal lymphopoietin. Conclusion AD is a heterogeneous disease both clinically and biologically. Four distinct clusters of patients with AD have been identified that could represent endotypes with unique biological mechanisms. Elucidation of these endotypes warrants further investigation and will require future intervention trials with specific agents, such as biologics.

Atopic dermatitis (AD), the most common chronic inflammatory skin disease, is driven by both terminal keratinocyte differentiation defects and strong type 2 immune responses. In contrast to chronic plaque-type psoriasis, AD is now understood to be a much more heterogeneous disease, with additional activation of TH22, TH17/IL-23, and TH1 cytokine pathways depending on the subtype of the disease. In this review we discuss our current understanding of the AD immune map in both patients with early-onset and those with chronic disease. Clinical studies with broad and targeted therapeutics have helped to elucidate the contribution of various immune axes to the disease phenotype. Importantly, immune activation extends well beyond lesional AD because nonlesional skin and the blood component harbor AD-specific inflammatory changes. For this reason, future therapeutics will need to focus on a systemic treatment approach, especially in patients with moderate-to-severe disease.

This review aims to highlight recently published articles on atopic dermatitis (AD). Updated are the insights into epidemiology, pathology, diagnostics, and therapy. Epidemiologic studies have revealed a positive correlation between AD and systemic conditions, such as rheumatoid arthritis, inflammatory bowel disease, and neonatal adiposity. Pathologic findings highlight the involvement of novel barrier factors (desmoplakin and claudin), novel immune cell subsets (pathogenic effector TH2 cells and group 2 innate lymphoid cells), and differential skewing of helper T cells (eg, TH17 dominance in Asians with AD). As diagnostics, noninvasive examinations of the transepidermal water loss of neonates, the density of epidermal Staphylococcus species, and the gut flora might prognosticate the onset of AD. As for therapy, various methods are proposed, including conventional (petrolatum and UV) and molecule-oriented regimens targeting Janus kinase, signal transducer and activator of transcription 3, extracellular signal-regulated kinase, sirtuin 1, or aryl hydrocarbon receptor.

Background Group 2 innate lymphoid cells (ILC2s) are the dominant innate lymphoid cell population in the lungs at steady state, and their release of type 2 cytokines is a central driver in responding eosinophil infiltration and increased airway hyperreactivity. Our laboratory has identified a unique subset of ILC2s in the lungs that actively produce IL-10 (ILC210s). Objective Our aim was to characterize the effector functions of ILC210s in the development and pathology of allergic asthma. Methods IL-4–stimulated ILC210s were isolated to evaluate cytokine secretion, transcription factor signaling, metabolic dependence, and effector functions in vitro. ILC210s were also adoptively transferred into Rag2–/–γc–/– mice, which were then challenged with IL-33 and assessed for airway hyperreactivity and lung inflammation. Results We have determined that the transcription factors cMaf and Blimp-1 regulate IL-10 expression in ILC210s. Strikingly, our results demonstrate that ILC210s can utilize both autocrine and paracrine signaling to suppress proinflammatory ILC2 effector functions in vitro. Further, this subset dampens airway hyperreactivity and significantly reduces lung inflammation in vivo. Interestingly, ILC210s demonstrated a metabolic dependency on the glycolytic pathway for IL-10 production, shifting from the fatty acid oxidation pathway conventionally utilized for proinflammatory effector functions. Conclusion These findings provide an important and previously unrecognized role of ILC210s in diseases associated with ILC2s such as allergic lung inflammation and asthma. They also provide new insights into the metabolism dependency of proinflammatory and anti-inflammatory ILC2 phenotypes.

Background Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that is important for the development of type 2 inflammatory responses at mucosal surfaces. Objective In humans, TSLP level has been found to be elevated in the lungs of patients with asthma, and in mouse models, TSLP can promote type 2 airway inflammation, primarily through the activation of dendritic cells. However, the mechanisms underlying its role remain unclear. The objective of this study was to provide a mechanistic analysis of TSLP-mediated type 2 airway inflammation Methods To dissect the mechanisms of TSLP-mediated type 2 responses, mice were treated with TSLP and antigen to evaluate cellular immune responses. Flow cytometric analyses were used to follow responses in the airways, and conditional deletion of TSLP receptor and adoptive transfer were used to identify the cellular subsets involved in this inflammatory response. Results We showed that TSLP can directly promote TH2-cell differentiation in the lung, independent of the draining lymph nodes. We also identified a population of patrolling monocytes/interstitial macrophages (IMs) (CD11c-expressing IMs) that are both necessary and sufficient for TSLP-mediated TH2-cell differentiation and airway inflammation. TH2-cell–driven airway eosinophilia is attenuated by ablation of CD11c-expressing IMs or by selective deficiency of TSLP receptor signaling in these cells. More importantly, CD11c-expressing IMs are sufficient for the induction of acute TH2-cell responses in the lungs that is independent of dendritic cells and T-cell priming in the draining lymph nodes. Conclusion These findings indicate a novel mechanistic role for TSLP and CD11c-expressing IMs in the development of acute TH2-cell–dependent allergic airway inflammation. This work also demonstrates a new role for TSLP in promoting type 2 responses directly in the lung.

Background Alopecia areata (AA) is a common T cell–mediated disorder with limited therapeutics. A molecular profile of cytokine pathways in AA tissues is lacking. Although studies have focused on T H 1/IFN-γ responses, several observations support a shared genetic background between AA and atopy. Objective We sought to define the AA scalp transcriptome and associated biomarkers with comparisons with atopic dermatitis (AD) and psoriasis. Methods We performed microarray and RT-PCR profiling of 27 lesional and 17 nonlesional scalp samples from patients with AA for comparison with normal scalp samples (n = 6). AA gene expression was also compared with samples from patients with lesional or nonlesional AD and those with psoriasis. A fold change of greater than 1.5 and a false discovery rate of less than 0.05 were used for differentially expressed genes (DEGs). Results We established the AA transcriptomes (lesional vs nonlesional: 734 DEGs [297 upregulated and 437 downregulated]; lesional vs normal: 4230 DEGs [1980 upregulated and 2250 downregulated]), including many upregulated immune and downregulated hair keratin genes. Equally impressive as upregulation in T H 1/interferon markers ( IFNG and CXCL10/CXCL9 ) were those noted in T H 2 ( IL13 , CCL18, CCL26 , thymic stromal lymphopoietin, and periostin), T H 9/IL-9, IL-23 (p40 and p19), and IL-16 mediators (all P H 17/T H 22 markers. Hair keratin (KRT) expressions (ie, KRT86 and KRT85 ) were significantly suppressed in lesional skin. Greater scalp involvement (>25%) was associated with greater immune and keratin dysregulation and larger abnormalities in nonlesional scalp samples (ie, CXCL10 and KRT85 ). Conclusions Our data associate the AA signature with T H 2, T H 1, IL-23, and IL-9/T H 9 cytokine activation, suggesting consideration of anti-T H 2, anti-T H 1, and anti–IL-23 targeting strategies. Similar to psoriasis and AD, clinical trials with selective antagonists are required to dissect key pathogenic pathways.

© 2015 American Academy of Allergy, Asthma & Immunology. The basis for the sudden and dramatic increase in atopic dermatitis (AD) and related atopic diseases in the second half of the 20th century is unclear. The hygiene hypothesis proposes that the transition from rural to urban living leads to reduced childhood exposure to pathogenic microorganisms. Hence instead of having the normal TH1 bias and immune tolerance because of repeated exposure to pathogens, urban dwellers have TH2 cell immune activity and atopic disease in a more sterile environment. Various other environmental exposures have been implicated in the explosion of AD (and atopic disorders in general), including breast-feeding, tobacco smoking, alcohol consumption, and exposure to domesticated furry pets. Notably, the key role of a compromised barrier of neonatal skin as a predisposing factor in the development of childhood AD has recently been demonstrated. In this article we review the salubrious effects of suberythemogenic doses of UVB irradiation for the skin barrier. We then discuss how the lack of sufficient UVB exposure could have contributed to the rapid increase in the incidence of AD in developed countries. This hypothesis offers a separate but not competing partial explanation, which should be viewed as not discounting the role of the etiopathogenic factors that also could influence the prevalence of atopic disorders.

Background Eosinophilic esophagitis (EoE) is an inflammatory disorder of the esophagus defined by eosinophil infiltration and tissue remodeling with resulting symptoms of esophageal dysfunction. TNF-related apoptosis-inducing ligand (TRAIL) promotes inflammation through upregulation of the E3 ubiquitin-ligase midline-1 (MID1), which binds to and deactivates the catalytic subunit of protein phosphatase 2Ac, resulting in increased nuclear factor κB activation. Objective We sought to elucidate the role of TRAIL in EoE. Methods We used Aspergillus fumigatus to induce EoE in TRAIL-sufficient (wild-type) and TRAIL-deficient (TRAIL −/− ) mice and targeted MID1 in the esophagus with small interfering RNA. We also treated mice with recombinant thymic stromal lymphopoietin (TSLP) and TRAIL. Results TRAIL deficiency and MID1 silencing with small interfering RNA reduced esophageal eosinophil and mast cell numbers and protected against esophageal circumference enlargement, muscularis externa thickening, and collagen deposition. MID1 expression and nuclear factor κB activation were reduced in TRAIL −/− mice, whereas protein phosphatase 2Ac levels were increased compared with those seen in wild-type control mice. This was associated with reduced expression of CCL24, CCL11, CCL20, IL-5, IL-13, IL-25, TGFB, and TSLP. Treatment with TSLP reconstituted hallmark features of EoE in TRAIL −/− mice and recombinant TRAIL induced esophageal TSLP expression in vivo in the absence of allergen. Post hoc analysis of gene array data demonstrated significant upregulation of TRAIL and MID1 in a cohort of children with EoE compared with that seen in controls. Conclusion TRAIL regulates MID1 and TSLP, inflammation, fibrosis, smooth muscle hypertrophy, and expression of inflammatory effector chemokines and cytokines in experimental EoE.

The recognition that there are some patients with features of asthma and chronic obstructive pulmonary disease (COPD) has highlighted the need to develop more specific treatments for these clinical phenotypes. Some patients with COPD have predominantly eosinophilic inflammation and might respond to high doses of inhaled corticosteroids and newly developed specific antieosinophil therapies, including blocking antibodies against IL-5, IL-13, IL-33, and thymic stromal lymphopoietin, as well as oral chemoattractant receptor-homologous molecule expressed on TH2 cells antagonists. Other patients have severe asthma or are asthmatic patients who smoke with features of COPD-induced inflammation and might benefit from treatments targeting neutrophils, including macrolides, CXCR2 antagonists, phosphodiesterase 4 inhibitors, p38 mitogen-activating protein kinase inhibitors, and antibodies against IL-1 and IL-17. Other patients appear to have largely fixed obstruction with little inflammation and might respond to long-acting bronchodilators, including long-acting muscarinic antagonists, to reduce hyperinflation. Highly selected patients with severe asthma might benefit from bronchial thermoplasty. Some patients with overlap syndromes can be conveniently treated with triple fixed-dose combination inhaler therapy with an inhaled corticosteroid, long-acting β2-agonist, and long-acting muscarinic antagonist, several of which are now in development. Corticosteroid resistance is a feature of asthma-COPD overlap syndrome, and understanding the various molecular mechanisms of this resistance has identified novel therapeutic targets and presented the prospect of therapies that can restore corticosteroid responsiveness.

Background Pulmonary fibrosis is characterized by excessive accumulation of collagen and α-smooth muscle actin in the lung. The key molecules that promote these phenotypes are of clinical interest. Objectives Thymic stromal lymphopoietin (TSLP) has been found at high levels in patients with asthma and idiopathic pulmonary fibrosis, and TSLP has been proposed as a primary driver of lung fibrotic disease. We asked whether tumor necrosis factor superfamily protein 14 (TNFSF14) (aka LIGHT) controls TSLP production to initiate fibrosis. Methods Expression of TSLP and initiation of pulmonary fibrosis induced by bleomycin were assessed in mice deficient in LIGHT. The ability of recombinant LIGHT, given intratracheally to naive mice, to promote TSLP and fibrosis was also determined. Results Genetic deletion of LIGHT abolished lung TSLP expression driven by bleomycin, accompanied by near-complete absence of accumulation of lung collagen and α-smooth muscle actin. Furthermore, recombinant LIGHT administered in vivo induced lung expression of TSLP in the absence of other inflammatory stimuli, and strikingly reproduced the primary features of bleomycin-driven disease in a TSLP-dependent manner. Blockade of LIGHT binding to either of its receptors, herpes virus entry mediator and lymphotoxin beta receptor, inhibited clinical symptoms of pulmonary fibrosis, and correspondingly both receptors were found on human bronchial epithelial cells, a primary source of TSLP. Moreover, LIGHT induced TSLP directly in human bronchial epithelial cells and synergized with IL-13 and TGF-β in vivo to promote TSLP in the lungs and drive fibrosis. Conclusions These results show that LIGHT is a profibrogenic cytokine that may be a key driver of TSLP production during the initiation and development of lung fibrotic disease.

Asthma is a complex and heterogeneous disease with several phenotypes, including an allergic asthma phenotype characterized by TH2 cytokine production and associated with allergen sensitization and adaptive immunity. Asthma also includes nonallergic asthma phenotypes, such as asthma associated with exposure to air pollution, infection, or obesity, that require innate rather than adaptive immunity. These innate pathways that lead to asthma involve macrophages, neutrophils, natural killer T cells, and innate lymphoid cells, newly described cell types that produce a variety of cytokines, including IL-5 and IL-13. We review the recent data regarding innate lymphoid cells and their role in asthma.

Background Atopic dermatitis (AD) is a common and chronic inflammatory skin disease of type 2 immunity. Keratinocyte-derived cytokines, including thymic stromal lymphopoietin (TSLP) and IL-33, are considered to induce the development of AD. Production of prostanoids, a family of lipid mediators, is increased in AD lesions. However, their physiologic functions remain to be clarified. Objectives We sought to elucidate the functions of prostanoids in the development of AD. Methods The roles of prostanoids were investigated in a mouse model of AD induced by repeated application of hapten and PAM212, a keratinocyte cell line. Results Application of indomethacin, which blocks prostanoid synthesis, leads to enhanced TSLP and IL-33 production in the skin, increased serum IgE levels, and exacerbation of skin inflammation in this AD model. The skin inflammation was attenuated in TSLP receptor–deficient mice but not in IL-33–deficient mice, and the indomethacin-enhanced type 2 immune responses were abolished in TSLP receptor–deficient mice. Indomethacin increased protease-activated receptor 2–mediated TSLP production in keratinocytes in vitro, and prostaglandin E2 reversed the increase in TSLP levels through its receptor, the prostaglandin E2 receptor (EP2), by downregulating surface expression of protease-activated receptor 2. Administration of an EP2 agonist canceled indomethacin-enhanced TSLP production and type 2 immune responses in the skin, whereas an EP2 antagonist caused an enhancement of TSLP production and type 2 immune responses in the skin. Conclusion Prostaglandin E2–EP2 signaling negatively regulates murine AD-like skin inflammation by suppressing TSLP expression.

Background Fc receptor γ subunit (FcRγ)-related receptors expressed on antigen-presenting cells (APCs) enhance allergen sensitization and allergic inflammation. DNA demethylation of the high-affinity IgE receptor γ subunit gene (FCER1G) leads to FcRγ and FceRI overexpression on monocytes from patients with atopic dermatitis. Objective We investigated epigenetic mechanisms underlying FCER1G demethylation and upregulation of FcRγ-related receptors on APCs and the consequent effect on allergic responses. Methods Effects of thymic stromal lymphopoietin (TSLP) on expression of FcRγ and its related receptors and methylation or hydroxymethylation of FCER1G in human monocytes were assessed. Recruitment of ten-eleven translocation protein (TET) 2 to FCER1G by TSLP-activated phosphorylated signal transducer and activator of transcription 5 (pSTAT5) was evaluated. Effects of TSLP on expression of FcRγ-related receptors and costimulatory receptors on monocyte-derived dendritic cells (DCs) and the ability of DCs to take up ovalbumin were analyzed. TSLP-induced TH polarization and related cytokine production were also analyzed. Results pSTAT5 activation by TSLP resulted in TET2 recruitment to FCER1G, leading to FCER1G demethylation and subsequent upregulation of FcRγ-related receptors on monocytes. TSLP not only stimulated monocyte-derived DC maturation but also maintained their allergen uptake ability, likely through maintenance and upregulation of FcRγ-related receptors. Allergen sensitization and upregulation of TH2/TH17-related cytokines contributed to TSLP-DC–induced TH2/TH17 polarization. The latter was attenuated on neutralization with a dectin-2 antibody. Conclusions TSLP mediated upregulation of FcRγ-related receptors on APCs through activation of pSTAT5, which recruited TET2 to induce FCER1G demethylation. TSLP-induced allergic TH2/TH17 polarization likely depends on dectin-2–mediated allergen sensitization and upregulation of TH2/TH17-related cytokines.

Background Therapeutic normal IgG or intravenous immunoglobulin (IVIG) exerts anti-inflammatory effects through several mutually nonexclusive mechanisms. Recent data in mouse models of autoimmune disease suggest that IVIG induces IL-4 in basophils by enhancing IL-33 in SIGN-related 1–positive innate cells. However, translational insight on these data is lacking. Objective We sought to investigate the effect of IVIG on human basophil functions. Methods Isolated circulating basophils from healthy donors were cultured in the presence of IL-3, IL-33, GM-CSF, thymic stromal lymphopoietin, or IL-25. The effect of IVIG and F(ab')2 and Fc IVIG fragments was examined based on expression of various surface molecules, phosphorylation of spleen tyrosine kinase, induction of cytokines, and histamine release. Basophil phenotypes were also analyzed from IVIG-treated patients with myopathy. Approaches, such as depletion of anti-IgE reactivity from IVIG, blocking antibodies, or inhibitors, were used to investigate the mechanisms. Results We report that IVIG directly induces activation of IL-3–primed human basophils, but IL-33 and other cytokines were dispensable for this effect. Activation of basophils by IVIG led to enhanced expression of CD69 and secretion of IL-4, IL-6, and IL-8. IVIG-treated patients with myopathy displayed enhanced expression of CD69 on basophils. The spleen tyrosine kinase pathway is implicated in these functions of IVIG and were mediated by F(ab')2 fragments. Mechanistically, IVIG induced IL-4 in human basophils by interacting with basophil surface-bound IgE but independent of FcγRII, type II Fc receptors, C-type lectin receptors, and sialic acid–binding immunoglobulin-like lectins. Conclusion These results uncovered a pathway of promoting the TH2 response by IVIG through direct interaction of IgG with human basophils.

Background Group 2 innate lymphoid cells (ILC2s) are effective producers of IL-5 and IL-13 during allergic inflammation and bridge the innate and adaptive immune responses. ILC2 numbers are increased in asthmatic patients compared with healthy control subjects. Thus far, human data describing their phenotype during acute allergic inflammation in the lung are incomplete. Objectives This study aims to characterize and compare blood- and lung-derived ILC2s before and after segmental allergen challenge in patients with mild-to-moderate asthma with high blood eosinophil counts (>300 cells/mL). Methods ILC2s were isolated from blood and bronchoalveolar lavage (BAL) fluid before and after segmental allergen challenge. Cells were sorted by means of flow cytometry, cultured and analyzed for cytokine release or migration, and sequenced for RNA expression. Results ILC2s were nearly absent in the alveolar space under baseline conditions, but numbers increased significantly after allergen challenge (P < .05), whereas at the same time, ILC2 numbers in blood were reduced (P < .05). Prostaglandin D2 and CXCL12 levels in BAL fluid correlated with decreased ILC2 numbers in blood (P = .004, respective P = .024). After allergen challenge, several genes promoting type 2 inflammation were expressed at greater levels in BAL fluid compared with blood ILC2s, whereas blood ILC2s remain unactivated. Conclusion ILC2s accumulate at the site of allergic inflammation and are recruited from the blood. Their transcriptional and functional activation pattern promotes type 2 inflammation.

Objective: We set out to examine PG production in human ILC2s and the implications of such endogenous production on ILC2 function. Methods: The effects of the COX-1/2 inhibitor flurbiprofen, the he ...

In this study, we found Cystatin SN (CST1), a type 2 cystatin subfamily member, to be highly expressed in nasal polyps from patients with intractable chronic rhinosinusitis (CRS) with nasal polyps, using a whole-transcript analysis with next-generation sequencing. Eosinophilic CRS (ECRS) involves nasal polyps that are refractory and recur immediately after endoscopic sinus surgery. We hypothesized that CST1 may contribute to the pathogenesis of ECRS. We examined the expression of CST1 in nasal polyps from patients with ECRS by assessing mRNA expression levels using real-time PCR and immunohistochemistry. CST1 showed significantly greater expression in the epithelial cells of nasal polyps from patients with ECRS than in those from patients who did not have ECRS (non-ECRS). In particular, CST1 showed very strong expression in patients with severe ECRS. The expression of CST1 may be correlated with the recurrent and refractory nature of ECRS. We examined the function of CST1 using nasal epithelial cells and nasal fibroblasts. Stimulation by a combination of IL-4 plus double-stranded RNA plus CST1 significantly elevated mRNA expression levels and protein levels of TSLP in nasal epithelial cells. Stimulation by TSLP or IL-33 significantly elevated mRNA expression levels of CST1 in nasal epithelial cells. Stimulation of CST1 significantly elevated mRNA expression levels of CCL11 and POSTN in nasal fibroblasts. CST1 could amplify eosinophilic infiltration and T-helper cell type 2 inflammation by interacting with epithelial-derived cytokines and fibroblasts on nasal polyps. CST1 may be involved in the pathogenesis of ECRS, and may contribute to the severity and recurrence of CRS with nasal polyps after endoscopic sinus surgery.

Background: Influenza virus triggers severe asthma exacerbations for which no adequate treatment is available. It is known that IL-33 levels correlate with exacerbation severity, but its role in the immunopathogenesis of exacerbations has remained elusive. Objective: We hypothesized that IL-33 is necessary to drive asthma exacerbations. We intervened with the IL-33 cascade and sought to dissect its role, also in synergy with thymic stromal lymphopoietin (TSLP), in airway inflammation, antiviral activity, and lung function. We aimed to unveil the major source of IL-33 in the airways and IL-33–dependent mechanisms that underlie severe asthma exacerbations. Methods: Patients with mild asthma were experimentally infected with rhinovirus. Mice were chronically exposed to house dust mite extract and then infected with influenza to resemble key features of exacerbations in human subjects. Interventions included the anti–IL-33 receptor ST2, anti–TSLP, or both. Results: We identified bronchial ciliated cells and type II alveolar cells as a major local source of IL-33 during virus-driven exacerbation in human subjects and mice, respectively. By blocking ST2, we demonstrated that IL-33 and not TSLP was necessary to drive exacerbations. IL-33 enhanced airway hyperresponsiveness and airway inflammation by suppressing innate and adaptive antiviral responses and by instructing epithelial cells and dendritic cells of house dust mite–sensitized mice to dampen IFN-β expression and prevent the TH1-promoting dendritic cell phenotype. IL-33 also boosted luminal NETosis and halted cytolytic antiviral activities but did not affect the TH2 response. Conclusion: Interventions targeting the IL-33/ST2 axis could prove an effective acute short-term therapy for virus-induced asthma exacerbations.

Background Atopic dermatitis (AD) is a highly prevalent chronic inflammatory skin disease that is known to be, at least in part, genetically determined. Mutations in caspase recruitment domain-containing protein 14 (CARD14) have been shown to result in various forms of psoriasis and related disorders. Objective We aimed to identify rare DNA variants conferring a significant risk for AD through genetic and functional studies in a cohort of patients affected with severe AD. Methods Whole-exome and direct gene sequencing, immunohistochemistry, real-time PCR, ELISA, and functional assays in human keratinocytes were used. Results In a cohort of patients referred with severe AD, DNA sequencing revealed in 4 patients 2 rare heterozygous missense mutations in the gene encoding CARD14, a major regulator of nuclear factor κB (NF-κB). A dual luciferase reporter assay demonstrated that both mutations exert a dominant loss-of-function effect and result in decreased NF-κB signaling. Accordingly, immunohistochemistry staining showed decreased expression of CARD14 in patients' skin, as well as decreased levels of activated p65, a surrogate marker for NF-κB activity. CARD14-deficient or mutant-expressing keratinocytes displayed abnormal secretion of key mediators of innate immunity. Conclusions Although dominant gain-of-function mutations in CARD14 are associated with psoriasis and related diseases, loss-of-function mutations in the same gene are associated with a severe variant of AD.