Experimental gastrointestinal allergy enhances pulmonary responses to specific and unrelated allergens.

BACKGROUND: Gastrointestinal allergy often precedes or coexists with respiratory allergy. OBJECTIVE: We hypothesized that established experimental gastrointestinal allergy would prime for the development of allergic respiratory responses. METHODS: BALB/c mice were sensitized with ovalbumin (OVA) in the presence of aluminum potassium sulfate and then subjected to intragastric saline or OVA challenges. After the development of allergen-induced gastrointestinal allergy, mice were intranasally exposed to either saline, OVA, or a neoaeroallergen house dust mite (HDM) extract. Airway inflammation (eg, bronchoalveolar lavage fluid cellularity, cytokine levels, and OVA-specific antibody levels) and airway responsiveness to methacholine exposure were assessed after intranasal allergen exposure. RESULTS: A single intranasal exposure to OVA induced significantly more airway inflammation in intragastric OVA-challenged mice compared with that seen in intragastric saline-treated mice. Kinetic analysis revealed that the observed amplification of lung inflammation was sustained for up to 12 days after the last intragastric OVA challenge after resolution of blood eosinophilia. When mice with gastrointestinal allergy were repeatedly challenged with HDM in the respiratory tract, they experienced enhanced airway inflammation, including bronchoalveolar lavage fluid eosinophilia and increased IL-13 levels. CONCLUSION: Taken together, our results demonstrate that OVA-induced gastrointestinal allergy enhances not only allergic airway responses to OVA but also to HDM, an unrelated aeroallergen. CLINICAL IMPLICATIONS: Experimental gastrointestinal allergy primes for responses to allergens in the respiratory tract, enhancing antigen-specific antibody and T(H)2 cytokine production, airway inflammation, and airway hyperresponsiveness.

Epicutaneous aeroallergen exposure induces systemic TH2 immunity that predisposes to allergic nasal responses.

BACKGROUND: Atopic individuals are predisposed to mounting vigorous T(H)2-type immune responses to environmental allergens. The skin is often the first organ that manifests allergic disease and may provide an early entry point for antigen sensitization. OBJECTIVE: We sought to determine whether epicutaneous exposure to the aeroallergen Aspergillus fumigatus induces nasal allergic responses. Furthermore, we aimed to examine the mechanism involved. METHODS: Wild-type and signal transducer and activator of transcription 6 (STAT6)-deficient mice were exposed to epicutaneous A fumigatus and control antigen ovalbumin. Nasal inflammation and responsiveness to methacholine were monitored. RESULTS: Exposure to epicutaneous A fumigatus antigen induced a marked atopic dermatitis-like phenotype in a manner significantly more efficient than epicutaneous ovalbumin. A single A fumigatus intranasal challenge induced clinical nasal responses and hyperresponsiveness to methacholine in the nose as manifested by nasal symptoms, accompanied by allergic airway and nasal inflammation. Mechanistic analysis using gene-targeted mice revealed that the clinical nasal responses and hyperresponsiveness were STAT6-dependent. Although STAT6 was required for changes in nasal responses, it was not required for epicutaneous pathology except eosinophilia. CONCLUSION: Epicutaneous exposure to the aeroallergen A fumigatus potently primes for STAT6-dependent nasal responses. These results draw attention to the cooperative interaction between the nasal tract and skin. CLINICAL IMPLICATIONS: The skin is a potent site for antigen sensitization in the development of experimental allergic rhinitis.

The FIP1L1-PDGFRA fusion gene cooperates with IL-5 to induce murine hypereosinophilic syndrome (HES)/chronic eosinophilic leukemia (CEL)-like disease.

Dysregulated tyrosine kinase activity by the Fip1-like1 (FIP1L1)-platelet-derived growth factor receptor alpha (PDGFRA) (F/P) fusion gene has been identified as a cause of clonal hypereosinophilic syndrome (HES), called F/P-positive chronic eosinophilic leukemia (CEL) in humans. However, transplantation of F/P-transduced hematopoietic stem cells/progenitors (F/P(+) HSCs/Ps) into mice results in a chronic myelogenous leukemia-like disease, which does not resemble HES. Because a subgroup of patients with HES show T-cell-dependent interleukin-5 (IL-5) overexpression, we determined if expression of the F/P fusion gene in the presence of transgenic T-cell IL-5 overexpression in mice induces HES-like disease. Mice that received a transplant of CD2-IL-5-transgenic F/P(+) HSC/Ps (IL-5Tg-F/P) developed intense leukocytosis, strikingly high eosinophilia, and eosinophilic infiltration of nonhematopoietic as well as hematopoietic tissues, a phenotype resembling human HES. The disease phenotype was transferable to secondary transplant recipients of a high cell dose, suggesting involvement of a short-term repopulating stem cell or an early myeloid progenitor. Induction of significant eosinophilia was specific for F/P since expression of another fusion oncogene, p210-BCR/ABL, in the presence of IL-5 overexpression was characterized by a significantly lower eosinophilia than IL-5Tg-F/P recipients. These results suggest that F/P is not sufficient to induce a HES/CEL-like disease but requires a second event associated with IL-5 overexpression.

Epicutaneous antigen exposure primes for experimental eosinophilic esophagitis in mice.

BACKGROUND & AIMS: Eosinophilic esophagitis (EE) is frequently associated with atopic disease, including dermatitis and asthma. Data are emerging that atopic skin may provide an early entry point for antigen sensitization. We aimed to test the hypothesis that epicutaneous exposure to antigen primes for subsequent respiratory antigen-induced EE. METHODS: Wild-type and genetically engineered mice were subjected to epicutaneous antigen sensitization and the development of experimental EE, and immune responses were examined. RESULTS: We show that exposure to antigen via the epicutaneous route primes for marked eosinophilic inflammation in the esophagus triggered by a single airway antigen challenge. The development of experimental EE is associated with significant skin eosinophilia, accelerated bone marrow eosinophilopoiesis, blood eosinophilia, and large increases in serum antigen-specific immunoglobulin G1/immunoglobulin E using ovalbumin or Aspergillus fumigatus as the epicutaneous antigen. Mechanistic analysis with gene-targeted mice showed that interleukin-5 was required for esophageal eosinophilia and that interleukin-4, interleukin-13, and STAT6 contributed to a lesser extent. CONCLUSIONS: These findings provide the first evidence that epicutaneous exposure to allergens potently primes for EE via a Th2-dependent mechanism.

Identification of a cooperative mechanism involving interleukin-13 and eotaxin-2 in experimental allergic lung inflammation.

Pulmonary eosinophilia, a hallmark pathologic feature of allergic lung disease, is regulated by interleukin-13 (IL-13) as well as the eotaxin chemokines, but the specific role of these cytokines and their cooperative interaction are only partially understood. First, we elucidated the essential role of IL-13 in the induction of the eotaxins by comparing IL-13 gene-targeted mice with wild type control mice by using an ovalbumin-induced model of allergic airway inflammation. Notably, ovalbumin-induced expressions of eotaxin-1 and eotaxin-2 mRNA in the lungs were almost completely dependent upon IL-13. Second, in order to address the specific role of eotaxin-2 in IL-13-induced pulmonary eosinophilia, we generated eotaxin-2 gene-deficient mice by homologous recombination. Notably, in contrast to observations made in eotaxin-1-deficient mice, eotaxin-2-deficient mice had normal base-line eosinophil levels in the hematopoietic tissues and gastrointestinal tract. However, following intratracheal IL-13 administration, eotaxin-2-deficient mice showed a profound reduction in airway eosinophilia compared with wild type mice. Most interestingly, the level of peribronchial lung tissue eosinophils in IL-13-treated eotaxin-2-deficient mice was indistinguishable from wild type mice. Furthermore, IL-13 lung transgenic mice genetically engineered to be deficient in eotaxin-2 had a marked reduction of luminal eosinophils. Mechanistic analysis identified IL13-induced eotaxin-2 expression by macrophages in a distinct lung compartment (luminal inflammatory cells) compared with eotaxin-1, which was expressed solely in the tissue. Taken together, these results demonstrate a cooperative mechanism between IL-13 and eotaxin-2. In particular, IL-13 mediates allergen-induced eotaxin-2 expression, and eotaxin-2 mediates IL-13-induced airway eosinophilia.