These cells were first identified in single-cell studies as KRT17+/KRT5- basaloid cells in human idiopathic pulmonary fibrosis (IPF) lungs (Habermann et al., 2020) and independently shown by in vitro studies to arise from AT2 cells (Kathiriya et al., 2022). This evidence concerns the gene KRT5 and idiopathic pulmonary fibrosis.