Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Cell Biology, NECROSIS-FACTOR-ALPHA, URINARY-TRACT-INFECTION, DENDRITIC CELLS, MATRIX METALLOPROTEINASES, FACTOR THERAPY, IL-8 RECEPTOR, GELATINASE-B, BONE-MARROW, IN-VITRO, BACTERIAL, Animals, Antigens, Ly, Bacterial Infections, Chemokine CXCL2, Female, Immune System Diseases, Kinetics, Leukocyte Disorders, Macrophages, Matrix Metalloproteinase 9, Mice, Neutrophils, Specific Pathogen-Free Organisms, Tumor Necrosis Factor-alpha, Urinary Tract Infections, 06 Biological Sciences, 11 Medical and Health Sciences, Developmental Biology, 31 Biological sciences, 32 Biomedical and clinical sciences

Abstract:

The phagocytes of the innate immune system, macrophages and neutrophils, contribute to antibacterial defense, but their functional specialization and cooperation is unclear. Here, we report that three distinct phagocyte subsets play highly coordinated roles in bacterial urinary tract infection. Ly6C(-) macrophages acted as tissue-resident sentinels that attracted circulating neutrophils and Ly6C(+) macrophages. Such Ly6C(+) macrophages played a previously undescribed helper role: once recruited to the site of infection, they produced the cytokine TNF, which caused Ly6C(-) macrophages to secrete CXCL2. This chemokine activated matrix metalloproteinase-9 in neutrophils, allowing their entry into the uroepithelium to combat the bacteria. In summary, the sentinel macrophages elicit the powerful antibacterial functions of neutrophils only after confirmation by the helper macrophages, reminiscent of the licensing role of helper T cells in antiviral adaptive immunity. These findings identify helper macrophages and TNF as critical regulators in innate immunity against bacterial infections in epithelia.