As TGF-β is thought to play a central role in the development of pulmonary fibrosis and MAP3K19 is both highly expressed in BAL macrophages from IPF patients and in epithelial cells adjacent to fibrotic foci, we next examined whether inhibition of MAP3K19 kinase activity would affect TGF-β signal transduction. Here, MAP3K19 is linked to pulmonary fibrosis.