Fig. 1

Schematic illustration showing the progression of radiation-induced pneumopathy. Radiotherapy (RT) of the thoracic region can induce damage and death in epithelial and endothelial lung cells. Subsequent release of DAMPs, cytokines and chemokines leads to the recruitment of diverse immune cells into the lung tissue. An overwhelming cascade of pro-inflammatory cytokines secreted by activated immune cells can result in radiation-induced pneumonitis. During the progression of radiation-induced pneumopathy chronic inflammation, tissue hypoxia and growth factor release result in further microenvironmental changes in the lung tissue. Recruitment of fibrocytes and secretion of pro-fibrotic mediators trigger differentiation of fibroblasts from various sources including mesenchymal stem cells [250] and excessive deposition of extracellular matrix molecules (ECM) resulting in lung fibrosis