TLR9 and idiopathic pulmonary fibrosis: Further, fibroblasts derived from rapid progressor IPF lung biopsies were observed to have higher response to the TLR9 agonist, CpG-ODN, as compared to fibroblasts derived from slow progressor IPF lung biopsies (Trujillo et al., 2010b), suggesting that TLR9 signaling is enhanced in rapid progressor fibroblast and that this PRR might contribute to the enhanced progression of IPF in rapid progressor IPF patients.