[Role of eosinophilia in atopic pathology]

Atopy corresponds to a heightened predisposition to develop an IgE-mediated reaction to allergens in the environment. Symptomatic manifestations of atopy include skin disorders, rhinitis, and allergic asthma. Tissue infiltration by polynuclear eosinophils is a shared feature of all atopic diseases. In asthma, eosinophilic infiltration is considered as a pathognomonic finding, proportional to severity. Eosinophils have been linked directly to epithelial damage responsible for asthma symptoms as a result of massive production of basic proteins which are toxic for the mucosa. Eosinophils also produce fibrosis-inducing cytokines and contribute to remodeling of the airway. Activation of Th2 lymphocytes accounts for the influx of eosinophils into the airway via production not only of IL-5 but also of chemokines such as RANTES, MCP-3, and, above all, eotaxine. Resolution of airway inflammation in asthma is related to eosinophil apoptosis occurring spontaneously or therapeutically in response to anti-inflammatory agents. Based on current data, eosinophils can be considered as a pivotal factor in the occurrence of atopic manifestations and thus constitute a prime target for future immunotherapies.