Flagellin/TLR5 Stimulate Myeloid Progenitors to Enter Lung Tissue and to Locally Differentiate Into Macrophages

Toll-like receptor 5 (TLR5) is the of bacterial Flagellin. Reportedly, TLR5 engagement helps to combat infections, especially at mucosal sites, by evoking responses from epithelial cells and immune cells. Here we report that expressed on a previously defined bipotent progenitor macrophages (MΦs) osteoclasts (OCs) resides in mouse bone marrow (BM) circulates low frequency blood. In vitro , Flagellin promoted generation MΦs, but not OCs this progenitor. vivo MΦ/OC progenitors were recruited blood into lung upon intranasal inoculation Flagellin, where they rapidly differentiated MΦs. Recruitment was likely CCL2/CCR2 axis, since CCR2 type 2 alveolar (AECs) produced CCL2 stimulation Moreover, blockade reduced migration toward lavage fluid (LLF) Flagellin-inoculated mice. Our study points novel role Flagellin/TLR5 axis recruiting circulating infected tissue stimulating these locally differentiate The pathway produce MΦs may act, next monocyte recruitment, fortify host protection against infection sites.