Eosinophil-associated diseases (EADs)

Abstract

Eosinophils can be prominent in virtually any tissue during inflammatory responses increasing in number as a constituent of mixed inflammation or being the predominant or even the only cell found in inflammatory infiltrates. Peripheral blood and tissue eosinophilia can occur in patients with varied allergic and inflammatory diseases, as well as diverse hematologic malignancies. Although the criteria to define eosinophilic disorders involve several aspects and have been refined, the terms eosinophil-associated diseases (EADs) or eosinophilic diseases are generally used to describe diseases characterized by the presence of eosinophil-rich inflammatory infiltrates and/or extensive extracellular deposition of eosinophil-derived proteins resulting in clinically relevant organ pathology. EADs encompasses a broad spectrum of diseases of different etiologies including allergies, gastrointestinal disorders, dermatoses, hypereosinophilic syndromes (HESs), infectious diseases, and neoplastic disorders. The purpose of this chapter is to illustrate the ultrastructure of eosinophils participating in a wide variety of human diseases. We show which are the ultrastructural characteristics exhibited by human eosinophils in selected EADs affecting several tissues and organ systems. The identification of eosinophils participating in diseases, as well as their ultrastructural alterations, is important for diagnostic purposes and understanding the immunobiology of these enigmatic cells.