CHI3L1 and pulmonary fibrosis: 30,68 In mammalian lung fibrosis CHI3L1 plays a profibrotic role in the repair phase by augmenting alternative macrophage activation, fibroblast proliferation, and matrix deposition.163 Additionally, CHI3L1 exacerbates HPS-associated pulmonary fibrosis through binding to CRTH2 receptor.31,97 Serum CHI3L1 levels are also increased in patients with cystic fibrosis164 as well as asbestosis.165