RGS2 and idiopathic pulmonary fibrosis: Indeed, when HFL1 cells were exposed to thrombin, a protease elevated in bronchial alveolar lavage fluid of IPF patients [50], PFD treatment or direct overexpression of recombinant RGS2 to levels similar to those induced by PFD treatment can trigger several anti-fibrotic responses in HFL1 cells.