CHI3L1 and idiopathic pulmonary fibrosis: Although several soluble molecules and bronchoalveolar lavage fluid (BALF) marker, including CXCL11 [54], KL-6 [55], IL-7 [56], and YKL-40 [57], for IPF have been investigated, however, there is an urgent need to discover new biomarkers to predict the clinical outcome of IPF patients after lung transplantation.