KRT15 and idiopathic pulmonary fibrosis: The aberrant basaloid cells express some typical basal cell markers including TP63 and KRT17, but lack others such as KRT5 and KRT15, and also express multiple markers of cellular senescence and epithelial-mesenchymal transition, the highest expression of the IPF biomarker MMP7, and elevated expression of the TGF-β activator integrin αVβ6.