CHI3L1 and idiopathic pulmonary fibrosis: It should be noted that many other proteins, such as Defensins, S100A12, and Chitinase-3-like protein 1 (YKL-40), which are closely related to the innate immune system, were also found to be potential biomarkers for acute exacerbation, poor survival, and worse functional status in IPF [44, 45].