Eosinophils are involved in the initiation and progression of pulmonary inflammation releasing several cytotoxic proteins stored in their secretory granules such as eosinophil peroxidase (EPO), eosinophil major basic protein (EMBP) and eosinophil cationic protein (ECP) (81) (Figure 3Bii). About 40-50% increase in BALF eosinophilia has been associated with IPF patients, making it as a potential marker of progressive lung diseases including IPF (82–84). Here, EPX is linked to idiopathic pulmonary fibrosis.