As a matter of fact, when thrombin is contacted with human fetal lung fibroblast 1 (HFL1) cells, a protease is increased in bronchial alveolar lavage fluid of idiopathic pulmonary fibrosis (IPF) patients [109], while direct up-regulation of RGS2 expression to the levels comparable to those increased by PFD treatment can cause a series of anti-fibrotic responses in human lung HFL1 cells. Here, RGS2 is linked to idiopathic pulmonary fibrosis.