PTGS2 and idiopathic pulmonary fibrosis: Moreover, COX-2 expression and PGE2 production are markedly reduced in fibroblasts from IPF lung (F-IPFs; ref. 20) and PGE2 in bronchoalveolar lavage fluid (21) and COX-2 expression in lung biopsy specimens (22) are also reduced in patients with IPF.