Thymic stromal lymphopoietin-mediated extramedullary hematopoiesis promotes allergic inflammation.

Extramedullary hematopoiesis (EMH) refers to the differentiation of hematopoietic stem cells (HSCs) into effector cells that occurs in compartments outside of the bone marrow. Previous studies linked pattern-recognition receptor (PRR)-expressing HSCs, EMH, and immune responses to microbial stimuli. However, whether EMH operates in broader immune contexts remains unknown. Here, we demonstrate a previously unrecognized role for thymic stromal lymphopoietin (TSLP) in promoting the population expansion of progenitor cells in the periphery and identify that TSLP-elicited progenitors differentiated into effector cells including macrophages, dendritic cells, and granulocytes and that these cells contributed to type 2 cytokine responses. The frequency of circulating progenitor cells was also increased in allergic patients with a gain-of-function polymorphism in TSLP, suggesting the TSLP-EMH pathway might operate in human disease. These data identify that TSLP-induced EMH contributes to the development of allergic inflammation and indicate that EMH is a conserved mechanism of innate immunity.

MHC class II-dependent basophil-CD4+ T cell interactions promote T(H)2 cytokine-dependent immunity.

Dendritic cells can prime naive CD4+ T cells; however, here we demonstrate that dendritic cell-mediated priming was insufficient for the development of T helper type 2 cell-dependent immunity. We identify basophils as a dominant cell population that coexpressed major histocompatibility complex class II and interleukin 4 message after helminth infection. Basophilia was promoted by thymic stromal lymphopoietin, and depletion of basophils impaired immunity to helminth infection. Basophils promoted antigen-specific CD4+ T cell proliferation and interleukin 4 production in vitro, and transfer of basophils augmented the population expansion of helminth-responsive CD4+ T cells in vivo. Collectively, our studies suggest that major histocompatibility complex class II-dependent interactions between basophils and CD4+ T cells promote T helper type 2 cytokine responses and immunity to helminth infection.

Effects of an anti-TSLP antibody on allergen-induced asthmatic responses.

BACKGROUND: Thymic stromal lymphopoietin (TSLP) is an epithelial-cell-derived cytokine that may be important in initiating allergic inflammation. AMG 157 is a human anti-TSLP monoclonal immunoglobulin G2λ that binds human TSLP and prevents receptor interaction. METHODS: In this double-blind, placebo-controlled study, we randomly assigned 31 patients with mild allergic asthma to receive three monthly doses of AMG 157 (700 mg) or placebo intravenously. We conducted allergen challenges on days 42 and 84 to evaluate the effect of AMG 157 in reducing the maximum percentage decrease in the forced expiratory volume in 1 second (FEV1). We also measured the fraction of nitric oxide in exhaled air, blood and sputum eosinophils, and airway hyperresponsiveness. The primary end point was the late asthmatic response, as measured 3 to 7 hours after the allergen challenge. RESULTS: AMG 157 attenuated most measures of allergen-induced early and late asthmatic responses. The maximum percentage decrease in the FEV1 during the late response was 34.0% smaller in the AMG-157 group than in the placebo group on day 42 (P=0.09) and 45.9% smaller on day 84 (P=0.02). In addition, patients receiving AMG 157 had significant decreases in levels of blood and sputum eosinophils before and after the allergen challenge and in the fraction of exhaled nitric oxide. There were 15 adverse events in the AMG-157 group, as compared with 12 in the placebo group; there were no serious adverse events. CONCLUSIONS: Treatment with AMG 157 reduced allergen-induced bronchoconstriction and indexes of airway inflammation before and after allergen challenge. These findings are consistent with a key role for TSLP in allergen-induced airway responses and persistent airway inflammation in patients with allergic asthma. Whether anti-TSLP therapeutics will have clinical value cannot be determined from these data. (Funded by Amgen; ClinicalTrials.gov number, NCT01405963.).

TSLP promotes interleukin-3-independent basophil haematopoiesis and type 2 inflammation.

CD4(+) T-helper type 2 (T(H)2) cells, characterized by their expression of interleukin (IL)-4, IL-5, IL-9 and IL-13, are required for immunity to helminth parasites and promote the pathological inflammation associated with asthma and allergic diseases. Polymorphisms in the gene encoding the cytokine thymic stromal lymphopoietin (TSLP) are associated with the development of multiple allergic disorders in humans, indicating that TSLP is a critical regulator of T(H)2 cytokine-associated inflammatory diseases. In support of genetic analyses, exaggerated TSLP production is associated with asthma, atopic dermatitis and food allergies in patients, and studies in murine systems demonstrated that TSLP promotes T(H)2 cytokine-mediated immunity and inflammation. However, the mechanisms through which TSLP induces T(H)2 cytokine responses remain poorly defined. Here we demonstrate that TSLP promotes systemic basophilia, that disruption of TSLP-TSLPR interactions results in defective basophil responses, and that TSLPR-sufficient basophils can restore T(H)2-cell-dependent immunity in vivo. TSLP acted directly on bone-marrow-resident progenitors to promote basophil responses selectively. Critically, TSLP could elicit basophil responses in both IL-3-IL-3R-sufficient and -deficient environments, and genome-wide transcriptional profiling and functional analyses identified heterogeneity between TSLP-elicited versus IL-3-elicited basophils. Furthermore, activated human basophils expressed TSLPR, and basophils isolated from eosinophilic oesophagitis patients were distinct from classical basophils. Collectively, these studies identify previously unrecognized heterogeneity within the basophil cell lineage and indicate that expression of TSLP may influence susceptibility to multiple allergic diseases by regulating basophil haematopoiesis and eliciting a population of functionally distinct basophils that promote T(H)2 cytokine-mediated inflammation.

IL-17RA Signaling in Airway Inflammation and Bronchial Hyperreactivity in Allergic Asthma.

Asthma is a heterogeneous disease characterized by airway inflammation and hyperreactivity. IL-17 receptor A (IL-17RA) is a shared receptor subunit required for activity of IL-17 family cytokines, including IL-17A and IL-25. IL-17A and IL-25 induce different proinflammatory responses, and concentrations are elevated in subjects with asthma. However, the individual contributions of IL-17A and IL-25 to disease pathogenesis are unclear. We explored proinflammatory activities of the IL-17 pathway in models of pulmonary inflammation and assessed its effects on contractility of human bronchial airway smooth muscle. In two mouse models, IL-17RA, IL-17RB, or IL-25 blockade reduced airway inflammation and airway hyperreactivity. Individually, IL-17A and IL-25 enhanced contractility of human bronchial smooth muscle induced by methacholine or carbachol. IL-17A had more pronounced effects on methacholine-induced contractility in bronchial rings from donors with asthma compared with donors without asthma. Blocking the IL-17 pathway via IL-17RA may be a useful therapy for some patients with asthma by reducing pulmonary inflammation and airway hyperreactivity.

Cutting edge: allergen-specific CD4 T cells respond indirectly to thymic stromal lymphopoietin to promote allergic responses in the skin.

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that has been implicated in the initiation of allergic responses. CD4 T cells and dendritic cells are able to respond to TSLP in vitro; however, there has not been a careful dissection of the spatiotemporal response to TSLP by CD4 T cells in vivo during an allergic response. Previous work has suggested a requirement for TSLP in amplifying Th2 responses during allergen challenge by direct action on CD4 T cells; however, these studies did not determine whether there is an effect of TSLP on CD4 T cells during allergen sensitization. In this study we demonstrate an indirect role for TSLP on CD4 T cells during sensitization and challenge phases of an allergic response. This indirect effect of TSLP on CD4 T cells is due in part to the presence of TSLP exclusively in the allergen-sensitized and -challenged skin, rather than the draining lymph nodes.

Thymic stromal lymphopoietin amplifies the differentiation of alternatively activated macrophages.

The epithelial-derived cytokine thymic stromal lymphopoietin (TSLP) has been associated with the promotion of type 2 inflammation and the induction of allergic disease. In humans TSLP is elevated in the lungs of asthma patients and in the lesional skin of individuals with atopic dermatitis, whereas mice lacking TSLP responses are refractory to models of Th2-driven allergic disease. Although several cell types, including dendritic cells, basophils, and CD4 T cells, have been shown to respond to TSLP, its role in macrophage differentiation has not been studied. Type 2 cytokines (i.e., IL-4 and IL-13) can drive the differentiation of macrophages into alternatively activated macrophages (aaMs, also referred to as M2 macrophages). This population of macrophages is associated with allergic inflammation. We therefore reasoned that TSLP/TSLPR signaling may be involved in the differentiation and activation of aaMs during allergic airway inflammation. In this study, we report that TSLP changes the quiescent phenotype of pulmonary macrophages toward an aaM phenotype during TSLP-induced airway inflammation. This differentiation of airway macrophages was IL-13-, but not IL-4-, dependent. Taken together, we demonstrate in this study that TSLP/TSLPR plays a significant role in the amplification of aaMΦ polarization and chemokine production, thereby contributing to allergic inflammation.

Exposure to food allergens through inflamed skin promotes intestinal food allergy through the thymic stromal lymphopoietin-basophil axis.

BACKGROUND: Exposure to food allergens through a disrupted skin barrier has been recognized as a potential factor in the increasing prevalence of food allergy. OBJECTIVE: We sought to test the immunologic mechanisms by which epicutaneous sensitization to food allergens predisposes to intestinal food allergy. METHODS: Mice were epicutaneously sensitized with ovalbumin or peanut on an atopic dermatitis-like skin lesion, followed by intragastric antigen challenge. Antigen-specific serum IgE levels and T(H)2 cytokine responses were measured by ELISA. Expression of type 2 cytokines and mast cell proteases in the intestine were measured by using real-time PCR. Accumulation of basophils in the skin and mast cells in the intestine was examined by using flow cytometry. In vivo basophil depletion was achieved by using diphtheria toxin treatment of Baso-DTR mice. For cell-transfer studies, the basophil population was expanded in vivo by means of hydrodynamic tail vein injection of thymic stromal lymphopoietin (TSLP) cDNA plasmid. RESULTS: Sensitization to food allergens through an atopic dermatitis-like skin lesion is associated with an expansion of TSLP-elicited basophils in the skin that promote antigen-specific T(H)2 cytokine responses, increased antigen-specific serum IgE levels, and accumulation of mast cells in the intestine, promoting the development of intestinal food allergy. Critically, disruption of TSLP responses or depletion of basophils reduced the susceptibility to intestinal food allergy, whereas transfer of TSLP-elicited basophils into intact skin promoted disease. CONCLUSION: Epicutaneous sensitization on a disrupted skin barrier is associated with accumulation of TSLP-elicited basophils, which are necessary and sufficient to promote antigen-induced intestinal food allergy.

Thymic stromal lymphopoietin-dependent basophils promote Th2 cytokine responses following intestinal helminth infection.

CD4(+) Th2 cytokine responses promote the development of allergic inflammation and are critical for immunity to parasitic helminth infection. Recent studies highlighted that basophils can promote Th2 cytokine-mediated inflammation and that phenotypic and functional heterogeneity exists between classical IL-3-elicited basophils and thymic stromal lymphopoietin (TSLP)-elicited basophils. However, whether distinct basophil populations develop after helminth infection and their relative contributions to anti-helminth immune responses remain to be defined. After Trichinella spiralis infection of mice, we show that basophil responses are rapidly induced in multiple tissue compartments, including intestinal-draining lymph nodes. Trichinella-induced basophil responses were IL-3-IL-3R independent but critically dependent on TSLP-TSLPR interactions. Selective depletion of basophils after Trichinella infection impaired infection-induced CD4(+) Th2 cytokine responses, suggesting that TSLP-dependent basophils augment Th2 cytokine responses after helminth infection. The identification and functional classification of TSLP-dependent basophils in a helminth infection model, coupled with their recently described role in promoting atopic dermatitis, suggests that these cells may be a critical population in promoting Th2 cytokine-associated inflammation in a variety of inflammatory or infectious settings. Collectively, these data suggest that the TSLP-basophil pathway may represent a new target in the design of therapeutic intervention strategies to promote or limit Th2 cytokine-dependent immunity and inflammation.

Nucleotide oligomerization domain-containing proteins instruct T cell helper type 2 immunity through stromal activation.

Although a number of studies have examined the development of T-helper cell type 2 (Th2) immunity in different settings, the mechanisms underlying the initiation of this arm of adaptive immunity are not well understood. We exploited the fact that immunization with antigen plus either nucleotide-binding oligomerization domain-containing proteins 1 (Nod1) or 2 (Nod2) agonists drives Th2 induction to understand how these pattern-recognition receptors mediate the development of systemic Th2 immune responses. Here, we show in bone-marrow chimeric mice that Nod1 and Nod2 expression within the stromal compartment is necessary for priming of effector CD4(+) Th2 responses and specific IgG1 antibodies. In contrast, sensing of these ligands by dendritic cells was not sufficient to induce Th2 immunity, although these cells contribute to the response. Moreover, we determined that CD11c(+) cells were the critical antigen-presenting cells, whereas basophils and B cells did not affect the capacity of Nod ligands to induce CD4(+) Th2 effector function. Finally, we found that full Th2 induction upon Nod1 and Nod2 activation was dependent on both thymic stromal lymphopoietin production by the stromal cells and the up-regulation of the costimulatory molecule, OX40 ligand, on dendritic cells. This study provides in vivo evidence of how systemic Th2 immunity is induced in the context of Nod stimulation. Such understanding will influence the rational design of therapeutics that could reprogram the immune system during an active Th1-mediated disease, such as Crohn's disease.

Thymic stromal lymphopoietin activity is increased in nasal polyps of patients with chronic rhinosinusitis.

BACKGROUND: Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with TH2-dominant inflammation. Thymic stromal lymphopoietin (TSLP) is a cytokine that triggers dendritic cell-mediated TH2 inflammatory responses and that enhances IL-1-dependent TH2 cytokine production in mast cells. Although increased TSLP mRNA levels have been found in nasal polyps (NPs), expression of TSLP protein and its function in patients with chronic rhinosinusitis (CRS) have not been fully explored. OBJECTIVES: The objective of this study was to investigate the role of TSLP in patients with CRS. METHODS: We investigated the presence and stability of TSLP protein in NPs using ELISA and Western blotting and investigated the function of TSLP in nasal tissue extracts with a bioassay based on activation of human mast cells. RESULTS: Although TSLP mRNA levels were significantly increased in NP tissue from patients with CRSwNP compared with uncinate tissue from patients with CRS or control subjects, TSLP protein was significantly decreased in NP tissue, as detected by using the commercial ELISA kit. We found that recombinant TSLP was time-dependently degraded by NP extracts, and this degradation was completely inhibited by a protease inhibitor cocktail, suggesting that TSLP is sensitive to tissue proteases. Interestingly, NP extract-treated TSLP had higher activity in mast cells, although the amount of full-length TSLP was reduced up to 85%. NP extracts significantly enhanced IL-1ß-dependent IL-5 production in mast cells compared with uncinate tissue homogenates, and responses were significantly inhibited by anti-TSLP, suggesting that NPs contain biologically relevant levels of TSLP activity. CONCLUSION: TSLP and its metabolic products might play an important role in the inflammation seen in patients with CRSwNP.

Thymic stromal lymphopoietin is released by human epithelial cells in response to microbes, trauma, or inflammation and potently activates mast cells.

Compelling evidence suggests that the epithelial cell-derived cytokine thymic stromal lymphopoietin (TSLP) may initiate asthma or atopic dermatitis through a dendritic cell-mediated T helper (Th)2 response. Here, we describe how TSLP might initiate and aggravate allergic inflammation in the absence of T lymphocytes and immunoglobulin E antibodies via the innate immune system. We show that TSLP, synergistically with interleukin 1 and tumor necrosis factor, stimulates the production of high levels of Th2 cytokines by human mast cells (MCs). We next report that TSLP is released by primary epithelial cells in response to certain microbial products, physical injury, or inflammatory cytokines. Direct epithelial cell-mediated, TSLP-dependent activation of MCs may play a central role in "intrinsic" forms of atopic diseases and explain the aggravating role of infection and scratching in these diseases.

Herpesvirus saimiri encodes a new cytokine, IL-17, which binds to a novel cytokine receptor.

Herpesvirus Saimiri gene 13 (HVS13) exhibits 57% identity with the predicted sequence of a T cell-derived molecule termed CTLA8. Recombinant HVS13 and CTLA8 stimulate transcriptional factor NF-kappaB activity and Interleukin-6 (IL-6) secretion in fibroblasts, and costimulate T cell proliferation. An HVS13.Fc fusion protein was used to isolate a cDNA encoding a novel receptor that also binds CTLA8. This receptor is unrelated to previously identified cytokine receptor families. A recombinant soluble receptor inhibited T cell proliferation and IL-2 production induced by PHA, concanavalin A (conA), and anti-TCR MAb. These results define CTLA8 and HVS13 as novel cytokines that bind to a novel cytokine receptor. We propose to call these molecules IL-17, vIL-17, and IL-17R, respectively.

Airway epithelial cells activate TH2 cytokine production in mast cells through IL-1 and thymic stromal lymphopoietin.

BACKGROUND: Airway epithelial cells are important regulators of innate and adaptive immunity. Although mast cells are known to play a central role in manifestations of allergic inflammation and are found in the epithelium in patients with T(H)2-related diseases, their role is incompletely understood. OBJECTIVES: The objective of this study was to investigate the role of airway epithelial cells in the production of T(H)2 cytokines in mast cells. METHODS: Normal human bronchial epithelial (NHBE) cells were stimulated with TNF, IL-4, IFN-γ, IL-17A, and double-stranded RNA (dsRNA) alone or in combination. Human mast cells were stimulated with epithelial cell-derived supernatants or cocultured with NHBE cells. T(H)2 cytokine responses were blocked with neutralizing antibodies. RESULTS: Supernatants from IL-4- and dsRNA-stimulated NHBE cells significantly enhanced T(H)2 cytokine production from mast cells. The combination of IL-4 and dsRNA itself or supernatants from NHBE cells stimulated with other cytokines did not activate mast cells, suggesting that mast cell responses were induced by epithelial cell factors that were only induced by IL-4 and dsRNA. Epithelial supernatant-dependent T(H)2 cytokine production in mast cells was suppressed by anti-IL-1 and anti- thymic stromal lymphopoietin (TSLP) and was enhanced by anti-IL-1 receptor antagonist. Similar results were observed in coculture experiments. Finally, we found dsRNA-dependent production of IL-1, TSLP, and IL-1 receptor antagonist in NHBE cells was regulated by T(H) cytokines, and their ratio in NHBE cells correlated with T(H)2 cytokine production in mast cells. CONCLUSIONS: Pathogens producing dsRNA, such as respiratory viral infections, might amplify local T(H)2 inflammation in asthmatic patients through the production of TSLP and IL-1 by epithelial cells and subsequent activation of T(H)2 cytokine production by mast cells in the airways.

Dibutyl phthalate-induced thymic stromal lymphopoietin is required for Th2 contact hypersensitivity responses.

Thymic stromal lymphopoietin (TSLP) is an IL-7-related cytokine, produced by epithelial cells, that has been linked to atopic dermatitis and asthma; however, it remains unclear how TSLP shapes the adaptive immune response that causes these allergic disorders. In this study, we demonstrate a role for TSLP in a Th2 model of contact hypersensitivity in mice. TSLP is required for the development of Th2-type contact hypersensitivity induced by the hapten FITC in combination with the sensitizing agent dibutyl phthalate. TSLPR-deficient mice exhibited a dramatically reduced response, including markedly reduced local infiltration by eosinophils, Th2 cytokine production, and serum IgE levels, following FITC sensitization and challenge. The reduced response by TSLPR-deficient mice is likely due to decreased frequency and reduced T cell stimulatory function of skin-derived Ag-bearing FITC(+)CD11c(+) dendritic cells in draining lymph nodes following FITC sensitization. These data suggest that skin-derived dendritic cells are direct or indirect targets of TSLP in the development of type 2 immune responses in the skin, where TSLP drives their maturation, accumulation in skin draining lymph nodes, and ability to induce proliferation of naive allergen-specific T cells.

Spontaneous atopic dermatitis in mice expressing an inducible thymic stromal lymphopoietin transgene specifically in the skin.

The cytokine thymic stromal lymphopoietin (TSLP) has recently been implicated in the pathogenesis of atopic dermatitis (AD) and other allergic diseases in humans. To further characterize its role in this disease process, transgenic mice were generated that express a keratinocyte-specific, tetracycline-inducible TSLP transgene. Skin-specific overexpression of TSLP resulted in an AD-like phenotype, with the development of eczematous lesions containing inflammatory dermal cellular infiltrates, a dramatic increase in Th2 CD4+ T cells expressing cutaneous homing receptors, and elevated serum levels of IgE. These transgenic mice demonstrate that TSLP can initiate a cascade of allergic inflammation in the skin and provide a valuable animal model for future study of this common disease.

TSLP conditions the lung immune environment for the generation of pathogenic innate and antigen-specific adaptive immune responses.

Thymic stromal lymphopoietin (TSLP) is crucial for the development of atopic diseases in humans and mice. Mice that express a lung-specific TSLP transgene (surfactant protein C promoter (SPC)-TSLP) develop a spontaneous and progressive asthma-like disease, suggesting that TSLP expression alone was sufficient for disease development. In this study, we show that, in fact, TSLP alone only causes a weak innate response that is insufficient for development of full airway inflammatory disease. Complete disease development requires both TSLP and antigenic stimulation. These data suggest that the spontaneous lung inflammation observed in SPC-TSLP mice reflects a TSLP-driven predisposition toward the development of aberrant responses against innocuous environmental Ags. This provides evidence that TSLP may act directly to induce susceptibility to the inappropriate allergic responses that characterize atopy and asthma. We additionally show that disease development requires CD4 T cells but not B cells. Further, we reveal a TSLP-driven innate response involving mucus overproduction and goblet cell metaplasia. Taken together, these data suggest a multifaceted model of TSLP-mediated airway inflammation, with an initial activation of resident innate immune cells, followed by activation of the adaptive immune system and full disease development. This study provides new insight into the unique features of the asthma pathology contributed by the innate and adaptive immune responses in response to TSLP stimulation.

Regulation of helminth-induced Th2 responses by thymic stromal lymphopoietin.

Thymic stromal lymphopoietin was recently identified as a master switch for the development of allergen-driven Th2 responses. However, the role of thymic stromal lymphopoietin (TSLP) in the development of helminth-induced Th2 responses is unclear. Here, using TSLPR(-/-) mice, we show that while TSLPR signaling participates in the development of Schistosoma mansoni egg-induced CD4(+) Th2 responses, it plays only a transient role in the development of Th2-dependent pathology in the lung, liver, and intestine. Studies conducted in a pulmonary granuloma model showed that while a reduction in IL-4/IL-13-dependent granulomatous inflammation and tissue eosinophilia was observed in TSLPR(-/-) mice undergoing a primary response, lesion formation was not affected during a secondary granulomatous response, even though IL-5 and IL-13 were modestly reduced in the knockout mice. To evaluate the importance of TSLPR signaling in the development of a chronic Th2-dependent response, TSLPR(-/-) mice were also infected with S. mansoni cercariae. Here, the only significant difference noted in TSLPR(-/-) mice was a modest decrease in liver fibrosis in acutely infected animals. The transient decrease in fibrosis was associated with increased production of the antifibrotic cytokine IFN-gamma and decreased production of the profibrotic cytokine IL-13. Although the altered cytokine response persisted in chronically infected TSLPR(-/-) mice, it failed to reduce granuloma formation or fibrosis, confirming that TSLPR signaling plays a limited role in the development of chronic Th2-dependent pathology. Collectively, these findings suggest that while TSLPR signaling serves a key role in allergen-driven Th2 responses, it exerts minor regulatory activity during this chronic helminth infection.

New paradigms in basophil development, regulation and function.

Emerging evidence has shown that basophils perform essential, non-redundant functions in multiple models of acute and chronic Th2 cytokine-dependent immunity and inflammation. In particular, recent studies have shown that basophils are rapidly recruited to the lymph nodes, can function as antigen-presenting cells and are critical for the induction of Th2 cell differentiation and the associated inflammatory responses after exposure to helminth parasites or allergens. In this review, we discuss recent studies that provide new insights into the pathways that control basophil development, regulation and effector function.

Reversal of thymic stromal lymphopoietin-induced airway inflammation through inhibition of Th2 responses.

Lung-specific thymic stromal lymphopoietin (TSLP) expression is sufficient for the development of an asthma-like chronic airway inflammatory disease. However, the nature of the downstream pathways that regulate disease development are not known. In this study, we used IL-4- and Stat6-deficient mice to establish the role of Th2-type responses downstream of TSLP. IL-4 deficiency greatly reduced, but did not eliminate, TSLP-induced airway hyperresponsiveness, airway inflammation, eosinophilia, and goblet cell metaplasia, while Stat6 deficiency eliminated these asthma-like symptoms. We further demonstrate, using the chronic model of TSLP-mediated airway inflammation, that blockade of both IL-4 and IL-13 responses, through administration of an anti-IL-4R alpha mAb, reversed asthma-like symptoms, when given to mice with established disease. Collectively these data provide insight into the pathways engaged in TSLP-driven airway inflammation and demonstrate that simultaneous blockade of IL-4 and IL-13 can reverse established airway disease, suggesting that this may be an effective approach for the therapy of Th2-mediated inflammatory respiratory disease.