FURIN and idiopathic pulmonary fibrosis: Considering the important role played by some of the crucial receptors and targets in COVID-19 37, we determined the protein expression of SARS-CoV-2 receptor Angiotensin Converting Enzyme 2 (ACE2) and aiding proteases like transmembrane protease serine protease-2 (TMPRSS-2) and spike protein furin in the lung homogenates of non-smokers, smokers, COPD and IPF subjects.