MAPK1 and idiopathic pulmonary fibrosis: Amongst the cytotoxic T cells, IFN-γ mediated signaling, regulation of natural killer cell and eosinophil chemotaxis, the ERK1/ERK2 cascade, and responses to IL-1 and tumor necrosis factor (TNF) were distinctly upregulated in IPF compared to SSc-ILD (Figures 3C, E, Supplemental File 3); identification of these pathways was largely driven by increased expression of numerous major histocompatibility complex (MHC) class II cell surface receptors and several chemokines in IPF cytotoxic T cells.