Depletion of eosinophils during sensitization but not challenge phase in mice blocks the development of food allergy early in life.

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.