Pathobiology and Regulation of Eosinophils, Mast Cells, and Basophils in Allergic Asthma

Eosinophilia is a hallmark of allergic disorders, including asthma, allergic rhinitis, and atopic dermatitis. The onset and maintenance of allergic inflammation in atopic adults involves the activation of selective hemopoietic processes and the migration of mature and immature eosinophils to allergic tissue, where these cells release mediators of inflammation that participate in the regulation of inflammation. Eosinophils function in close cooperation with basophils and mast cells in allergic tissue, where crosstalk between these central effector cells regulates the inflammatory process. This chapter will review the cellular events leading to the accumulation of eosinophils and their progenitors in the airways in allergic asthma, with a particular focus on models of allergen-induced allergic inflammation. Inhaled allergen challenges in allergic asthmatics have advanced understanding of the pathogenesis of allergen exposure leading to early and late asthmatic responses and the associated airway hyperresponsiveness and type 2 airway inflammation. This chapter will also discuss the mechanisms of commonly used asthma therapies on allergen-induced eosinophilia and compare the effects of novel therapies targeting specific immune pathways for a better understanding of how to regulate airway eosinophil levels in patients with asthma.