S100A9 and pulmonary fibrosis: In comparison to the neutrophilic cases, the IPA analysis of the proteomic datasets derived from horses with metachromatic inflammation revealed enrichment in pathways related to hypersensitivity reaction (CD44, ICAM1, SOD1, PSAP, CDH1) and lung fibrosis (AGER, TGFBR2, FBLN1, S100A9) (Figure 6).