In contrast, lung fibroblasts from IPF patients exhibit variable resistance to Fas-induced apoptosis (13, 15) due to downregulation of Fas expression (14, 17, 18) and increased expression of multiple antiapoptotic genes, including Bcl-2, XIAP, cFLIPL, and PTPN13 (11, 19–21). The gene discussed is FAS; the disease is idiopathic pulmonary fibrosis.