This schematic view of the morpho-functional unit of the lung (alveolus) depicts the main differences in cellular composition in idiopathic pulmonary fibrosis (IPF) and systemic sclerosis-associated interstitial lung disease (SSc-ILD) compared with normal p... This schematic view of the morpho-functional unit of the lung (alveolus) depicts the main differences in cellular composition in idiopathic pulmonary fibrosis (IPF) and systemic sclerosis-associated interstitial lung disease (SSc-ILD) compared with normal physiological cellular components. Th2: T-helper cell type 2; AEC: alveolar epithelial cell. Gianluca Bagnato, and Sergio Harari Eur Respir Rev 2015;24:102-114 ©2015 by European Respiratory Society