Toll-Like-Receptor 5 Reduces Lung Dysbiosis and Protects Against Pulmonary Fibrosis

IPF results from maladaptive responses to lung epithelial injury, but the underlying mechanisms remain unclear. Here, we show that deficiency in the innate immune receptor, toll-like receptor 5 (TLR5), is associated with IPF in humans and with increased susceptibility to experimental fibrosis in mice, while activation of lung epithelial TLR5 through a synthetic flagellin analog protects from experimental fibrosis.

Mechanistically, epithelial TLR5 activation induces antimicrobial gene expression and ameliorates dysbiosis after lung injury. In contrast, TLR5 deficiency in mice and IPF patients is associated with lung dysbiosis. Elimination of the microbiome in mice through antibiotics abolishes the protective effect of TLR5 and reconstitution of the microbiome rescues the observed phenotype.