Nerve associated lung resident interstitial macrophage subset exhibits distinct localization and polarization

Abstract Tissue resident macrophages are a diverse population of cells that perform specialized functions: sustaining tissue homeostasis and tissue surveillance. Here we report an interstitial subset of CD169+ lung resident macrophages that are transcriptionally and developmentally distinct from alveolar macrophages (AM). They are primarily localized around the airways and in close contact with the innervating pulmonary nerves. These nerve and airway associated macrophages (NAMs) are tissue resident, yolk sac derived, self-renewing, and do not require CCR2+ monocytes for development or maintenance. We show that unlike AMs, CSF-1, but not CSF-2 is required for their development. Bulk population and single cell transcriptome analysis indicates that NAMs are distinct from other lung resident macrophage subsets and highly expressed immune regulatory genes under steady state and inflammatory conditions. NAMs proliferated robustly following TLR activation and influenza infection, and in their absence, the inflammatory response was remarkably augmented resulting in excessive production of inflammatory cytokines and innate immune cell infiltration. We show that AMs contribute to viral clearance while NAMs, contribute to regulating virus-induced inflammation in the lung. Overall, our study relates structure to function at a fundamental level, and provides essential insights into a distinct subset of resident macrophages in the lung that function to maintain immune and tissue homeostasis.