We have previously proposed that the pathogenesis of eosinophilic esophagitis (EE) is mediated by an IL-13–driven epithelial cell response associated with marked gene dysregulation including eotaxin-3 overproduction. Herein, we compared epithelial responses between normal (NL) and EE patients aiming to uncover molecular explanations for EE pathogenesis. Esophageal epithelial cells could be maintained up to 5 passages, with 67% and 62% of cell lines reaching confluence in NL and EE, respectively. Both sets of epithelial cells avidly responded to IL-13 at similar levels as assessed by eotaxin-3 production. Acidic pH increased cellular release of eotaxin-3 (4.6 ± 1.98 ng/mL vs. 12.46 ± 2.90 ng/mL at pH 7.4 and 4 respectively, p<0.05). Numerous epidermal differentiation complex (EDC) genes, such as filaggrin, and SPRR3 were downregulated both in IL-13-stimulated esophageal epithelial cells and in EE biopsies compared to NL. While the filaggrin loss of function mutation 2282del4 was overrepresented in EE compared to control individuals (6.1% vs. 1.3% respectively, p=0.0172), the decreased filaggrin expression was uniformly seen in all EE patients in vivo. Indeed, expression of the EDC genes filaggrin and involucrin was strongly decreased directly by IL-13. These results establish that the epithelial response in EE involves a cooperative interaction between IL-13 and expression of EDC genes.

Background Eosinophilic esophagitis (EE) is an emerging worldwide disease that mimics gastroesophageal reflux disease. Objective Early studies have suggested that esophageal eosinophilia occurs in association with T helper type 2 allergic responses, yet the local and systemic expression of relevant cytokines has not been well characterized. Methods A human inflammatory cytokine and receptor PCR array containing 84 genes followed by PCR validation and multiplex arrays were used to quantify cytokine mRNA in esophageal biopsies and blood levels. Results Esophageal transcripts of numerous chemokines [e.g. CCL1, CCL23, CCL26 (eotaxin-3), CXCL1, and CXCL2], cytokines (e.g. IL13 and ABCF1), and cytokine receptors (e.g. IL5RA) were induced at least 4-fold in individuals with EE. Analysis of esophageal biopsies (n=288) revealed that eotaxin-3 mRNA level alone had 89% sensitivity for distinguishing EE from non-EE individuals. The presence of allergy was associated with significantly increased esophageal expression of IL4 and IL5 mRNA in active EE patients. We identified 8 cytokines (IL-4, IL-13, IL-5, IL-6, IL-12p70, CD40L, IL-1α, and IL-17) whose blood levels retrospectively distinguished 12 non-EE from 13 EE patients with 100% specificity and 100% sensitivity. When applied to a blinded, prospectively recruited group of 36 patients, the cytokine panel scoring system had a 79% positive predictive value, 68% negative predictive value, 61% sensitivity, and 83% specificity for identifying EE. Conclusion Evidence is presented that IL13 and IL5 associate with eosinophil and eotaxin-3 levels, indicating the key role of adaptive Th2 immunity in regulating eotaxin-3-driven esophageal eosinophilia in the absence of a consistent systemic change in cytokines.

IL-25 is a TH2-promoting cytokine, however, its role in regulating the maintenance and function of TH2 memory/effector cells in vivo remains elusive. We have developed a novel mouse model to study the regulation of TH2 memory/effector cells after re-exposure to OVA antigen. Phenotypic analyses reveal that the recalled TH2 memory/effector cells in lung express distinct level of IL-25 receptor (IL-25R), ST2, and OX40. Notably, the frequency of local IL-25R+CD4+ TH2 memory/effector cells in inflamed lung, but not other lymphoid tissues, is elevated after increased numbers of OVA antigen re-exposure. These lung resident IL-25R+CD4+ TH2 memory/effector cells are much more potent to produce TH2 cytokines than the TH2 cells in other lymphoid tissues. Enforced expression of IL-25R by T cells in mice resulted in increased accumulation of local antigen-specific TH2 memory/effector cells, leading to more prominent airway inflammation, compare to those of littermate controls in our novel mouse model of allergic lung diseases. These results suggest that IL-25 may promote allergic inflammation by enhancing the accumulation and function of lung resident IL-25R+CD4+ TH2 memory/effector cells in vivo.

Type-2 innate lymphoid cells (ILC2s) and acquired CD4+TH2 and TH17 cells were shown to contribute to the pathogenesis of allergic asthma; however, their relative roles in mounting antigen recall response that exacerbate chronic allergic asthma remain elusive. Here we reported that repeated OVA re-challenge induced significant increases of eosinophil, not neutrophil accumulation and serum OVA specific IgE and IgG1 in rested mice that previously developed allergic asthma. Subsequent analysis revealed that these rested mice with allergic asthma preferentially mounted elevated OVA specific CD4+TH2 cell response against intranasal OVA re-challenge, while the frequency of lung OVA specific TH17 cells or ILC2s remained constant. While ILC2s and TH17 cells developed normally, STAT6 KO mice that lacked TH2 cell compartment or mice ablated of CD4+ T cells failed to mount allergic recall response to OVA re-challenge. Notably, we observed that cocultured ILC2s could greatly enhance TH2 cytokine production by OVA specific TH2 cells after OVA stimulation ex vivo. Indeed, mice co-transferred with ILC2s and OVA specific TH2 cells exhibited significantly increased inflammatory cell infiltration and goblet cell hyperplasia, compared to those transferred with ILC2s or TH2 cells alone. Collectively, our results suggest that antigen re-exposures preferentially induce lung resident TH2 cells to mount antigen recall immune response that can be enhanced by ILC2s to exacerbate allergic inflammation

Food allergy is an IgE-mediated disorder manifested by uncontrolled type-2 immune response in the gastrointestinal tract. Little is known about the underlying mechanisms that drive the propensity to develop food-induced intestinal hypersensitivity. IL-25 is a distinct member of IL-17 inflammatory cytokine family, functioning at evoking type-2 inflammatory response. We aimed at investigating the involvements of IL-25 and its responding cells in the development of IgE-mediated experimental food allergy. We observed that IL-25 expression was rapidly elevated in the epithelium of inflamed duodenum before the onset of anaphylactic reaction to ingested allergens. Mice overexpressing intestinal IL-25 or deficient of IL-17RB displayed exacerbated or attenuated symptomatic features of IgE-mediated experimental food allergy, respectively. Subsequent analysis revealed that Lin-IL-17RB+ type-2 innate lymphoid cells (ILC2) that reside in the laminar propria of small intestine prior to the development of IgE-mediated experimental food allergy are the primary producers of Th2 cytokine, IL-5 and IL-13, in response to IL-25 stimulation. Furthermore, irradiated mice reconstituted with bone marrow cells that are deficient of RoRα or IL-17RB became resistant to developing IgE-mediated experimental food allergy. Our results suggest that intestinal ILC2 residents are poised to respond to induced IL-25 and function in promoting the development of IgE-mediated experimental food allergy.

IgE-mediated food allergy is manifested by an overactive T-helper 2 immune response to dietary antigens in the gastrointestinal (GI) tract. Interleukin (IL)-9 promote intestinal mastocytosis which allow the development of oral antigen-induced anaphylaxis. However, little is known about the primary cellular sources of IL-9 or the mechanisms that promote intestinal mastocytosis. Here, we report the identification of multifunctional IL-9-producing innate helper cells (IHC9) that secrete prodigious amounts of TH2 cytokines and mast cell protease-1 (MCPt-1) in response to IL-33 and antigen/IgE complex crosslinking, respectively. Repeated intragastric antigen challenge induces significant accumulations of both intestinal IHC9 and CD4+TH2 cells, which correlate positively with symptoms and susceptibility to oral antigen-induced anaphylaxis. IHC9 development requires T cells and IL-4R, not IL-9R, signaling. The failure of irradiated mice reconstituted with STAT6-deficient bone marrow to generate IHC9 was accompanied by reduced serum MCPt-1, intestinal TH2 inflammation, mastocytosis, and goblet cell hyperplasia and loss of allergic diarrhea. Furthermore, inhibition of food allergy symptoms in mice ablated of IHC9 by anti-FcϵRIα antibody treatment could be reversed by adoptive transfer of IHC9. Thus, IHC9 represent a new type of innate helper cell lineage and function in promoting intestinal TH2 inflammation and mastocytosis that drive IgE-mediated anaphylaxis.