Pulmonary and activation-regulated chemokine (PARC)/CCL18 is a significant, primarily indirect, modulator of fibrosis and is elevated in association with various fibrotic lung diseases, including scleroderma, hypersensitivity pneumonitis, idiopathic pulmonary fibrosis, asthma, and sarcoidosis. This evidence concerns the gene CCL18 and idiopathic pulmonary fibrosis.