[Idiopathic pulmonary fibrosis: from biopathology to treatment].

Alveolitis, accumulation of immune and inflammatory cells within the lower respiratory tract, is the key to the development of pulmonary fibrosis. Alveolitis is responsible for lung injury (due to release of oxidant and proteolytic enzymes) and exaggerated lung repair (due to proliferation of mesenchymal cells and imbalance of collagen synthesis). Rationale for the treatment of pulmonary fibrosis implies the knowledge of pathophysiology of the different steps of the fibrotic process.