Ever since the pioneering work of Paul Ehrlich at the end of the 19th century, physicians have been intrigued by the mysteries of the eosinophil. In addition to its important role in host defense, there is increasing evidence that the eosinophil is also capable of host lung cellular injury.1,2 When stimulated, eosinophils produce a number of potentially injurious substances, including major basic protein, eosinophilic cationic protein, eosinophil-derived neurotoxin, reactive oxygen species, peroxidase, and collagenase.1,3 Although eosinophil activation is incompletely understood, the cytokines interleukin-1, interleukin-3, interleukin-5, and granulocyte-macrophage colony-stimulating factor4-6 have recently been found to be involved in eosinophil growth, chemotaxis, and adhesion. When present in excessive numbers, eosinophils can serve as central mediators of a number of diseases involving many different organs, including the lung.
The eosinophilic lung syndromes encompass a wide variety of pulmonary disorders including interstitial lung diseases, infectious diseases, vasculitis, malignancies, drug reactions, obstructive
Allen JN, Davis WB. What Is Eosinophilic Pneumonia?. Arch Intern Med. 1992;152(9):1765-1766. doi:10.1001/archinte.1992.00400210007001