The main findings of this study are as follows: (1) the MrgD receptor is less expressed in the lung parenchyma of patients with IPF; (2) in contrast, the Mas and AT1 receptors are more highly expressed in the lungs of IPF patients; and (3) the Mas receptor is predominantly localized in the pulmonary bronchioles. The gene discussed is MAS1; the disease is idiopathic pulmonary fibrosis.