Cook‐Mills, Joan M.

Abstract Food allergy can be life threatening and often develops early in life, especially in infants and children with atopic dermatitis. Food allergy is induced in neonatal mice with skin barrier mutations (Flaky Tail, FT+/− mice with filaggrin and mattrin gene mutations) by epicutaneous sensitization with co-exposures to the food allergen peanut extract (PNE), the environmental allergen Alternaria alternata (Alt), and detergent (4% SDS); oral PNE-challenge induces anaphylaxis. Sensitization in these neonates also induces eosinophil infiltration into the skin and elevates skin expression of eotaxins (CCL11 and CCL24). However, roles for eosinophils in food allergy are not known. In this study, the iPhil+/− FT+/− pups, which have an inducible eosinophil-deficiency upon injection of diphtheria toxin (DTX), were sensitized and then received PNE by gavage to assess anaphylaxis. DTX depletion of eosinophils, during sensitization and oral PNE-challenge, blocked the recruitment and activation of mast cells, blocked the Alt+PNE-induced increase in plasma IL-33 and OSM, attenuated serum PNE-specific IgE/IgG1/IgG2b, and blocked oral-PNE-induced anaphylaxis. Anti-IL-5 depletion of eosinophils during sensitization/challenge also blocked anaphylaxis. When eosinophils were depleted during allergen-skin-sensitization and restored before oral PNE-challenge, anaphylaxis was blocked. In contrast, when eosinophils were present during allergen-skin-sensitization but then depleted during oral PNE-challenge, anaphylaxis was not blocked. Together, these data indicate that although eosinophils are not necessary during oral food allergen-induced anaphylaxis, eosinophils have a critical role during the development of food allergy early in life by regulating the sensitization-induced increase in mast cell numbers and food allergen-specific IgE.

Abstract Allergen-induced respiratory inflammation facilitates and/or elicits the extravasation of proinflammatory leukocytes by well-understood mechanisms that mediate the movement of multiple cell types. The nonspecific character of these pathways led us to hypothesize that circulating cancer cells use similar mechanisms, promoting secondary tumor formation at distal sites. To test this hypothesis, the frequency of metastasis to the lung as a function of allergic pulmonary inflammation was assessed following the i.v. injection of B16-F10 melanoma cells in mice. These studies showed that allergen-induced pulmonary inflammation resulted in a >3-fold increase in lung metastases. This increase was dependent on CD4+ T-cell activities; however, it occurred independent of the induced eosinophilia associated with allergen provocation. Interventional strategies showed that existing therapeutic modalities for asthma, such as inhaled corticosteroids, were sufficient to block the enhanced pulmonary recruitment of cancer cells from circulation. Additional mechanistic studies further suggested that the ability of circulating cancer cells to extravasate to surrounding lung tissues was linked to the activation of the vascular endothelium via one or more Gαi-coupled receptors. Interestingly, a survey of a clinical breast cancer surgical database showed that the incidence of asthma was higher among patients with lung metastases. Thus, our data show that allergic respiratory inflammation may represent a risk factor for the development of lung metastases and suggest that amelioration of the pulmonary inflammation associated with asthma will have a direct and immediate benefit to the 7% to 8% of breast cancer patients with this lung disease. [Cancer Res 2008;68(20):8582–9]

The trafficking of leukocytes from the blood to sites of inflammation is the cumulative result of receptor-ligand-mediated signaling events associated with the leukocytes themselves as well as with the underlying vascular endothelium. Our data show that Gα i signaling pathways in the vascular endothelium regulate a critical step required for leukocyte diapedesis. In vivo studies using knockout mice demonstrated that a signaling event in a non-lymphohematopoietic compartment of the lung prevented the recruitment of proinflammatory leukocytes. Intravital microscopy showed that blockade was at the capillary endothelial surface and ex vivo studies of leukocyte trafficking demonstrated that a Gα i -signaling event in endothelial cells was required for transmigration. Collectively, these data suggest that specific Gα i2 -mediated signaling between endothelial cells and leukocytes is required for the extravasation of leukocytes and for tissue-specific accumulation.