DNA methylation and histone modifications have been shown to be responsible for the differential expression of certain genes in pulmonary fibrosis.20, 22, 23 To examine whether such epigenetic mechanisms are responsible for the diminished expression of Fas in fibroblasts from bleomycin-injured mice, we first examined levels of DNA methylation near the transcription start site of Fas. The gene discussed is FAS; the disease is pulmonary fibrosis.