IHC analysis of IPF lungs demonstrated the presence of p16Ink4a+/ACTA2+ and p16Ink4a+/CTHRC1+ cells within areas of dense fibrotic remodeling and the absence of these cells in the normal control lungs (Figure 6E, Supplemental Figure 7C). The gene discussed is ACTA2; the disease is idiopathic pulmonary fibrosis.