Neutrophil Migration into the Infected Uroepithelium Is Regulated by the Crosstalk between Resident and Helper Macrophages

The antibacterial defense against infections depends on the cooperation between distinct phagocytes of the innate immune system, namely macrophages and neutrophils. However, the mechanisms driving this cooperation are incompletely understood. In this study we describe the crosstalk between Ly6C(+) and Ly6C(-) macrophage-subtypes and neutrophils in the context of urinary tract infection (UTI) with uropathogenic E. coli (UPEC). Ly6C(-) macrophages acted as tissue resident sentinels and attracted circulating phagocytes by chemokines. Ly6C(+) macrophages produced tumor necrosis factor (TNF) that licensed Ly6C(-) macrophages to release preformed CXCL2, which in turn caused matrix metalloproteinases (MMP-9) secretion by neutrophils to enable transepithelial migration.