CX3CL1 and pulmonary fibrosis: The aim of this study was to determine the level of CX3CL1 in the bronchoalveolar lavage fluid (BALF) of patients affected by particular DPLDs—pulmonary sarcoidosis (PS), idiopathic pulmonary fibrosis (IPF), hypersensitivity pneumonitis (HP) and connective tissue disease-associated interstitial lung disease (CTD-ILD).