S100A9 and idiopathic pulmonary fibrosis: S100A8 and S100A9 are upregulated in the acute exacerbations of idiopathic pulmonary fibrosis (IPF) suggesting roles of different signaling pathways like Clathrin-mediated endocytosis signaling, atherosclerosis signaling, and IL2 signaling in the pathogenesis of acute exacerbations of IPF [123].