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Published on: April 20, 2018
Immune surveillance of the lung by migrating tissue monocytes
Mathieu P Rodero1, Lucie Poupel1, Pierre-Louis Loyher1
1Centre d'Immunologie et des Maladies Infectieuses, University Pierre et Marie Curie, Sorbonne Universities, Paris, France.
Abstract:
Monocytes are phagocytic effector cells in the blood and precursors of resident and inflammatory tissue macrophages. The aim of the current study was to analyse and compare their contribution to innate immune surveillance of the lung in the steady state with macrophage and dendritic cells (DC). ECFP and EGFP transgenic reporters based upon Csf1r and Cx3cr1 distinguish monocytes from resident mononuclear phagocytes. We used these transgenes to study the migratory properties of monocytes and macrophages by functional imaging on explanted lungs. Migratory monocytes were found to be either patrolling within large vessels of the lung or locating at the interface between lung capillaries and alveoli. This spatial organisation gives to monocytes the property to capture fluorescent particles derived from both vascular and airway routes. We conclude that monocytes participate in steady-state surveillance of the lung, in a way that is complementary to resident macrophages and DC, without differentiating into macrophages.
Insights
Monocytes patrol lung vessels and capillaries, contributing to innate immune surveillance. These findings reveal a complementary role to resident macrophages and dendritic cells in lung immunity.
Area of Science:
- Immunology
- Cell Biology
- Respiratory Medicine
Background:
- Monocytes are blood cells that develop into macrophages and dendritic cells.
- Innate immune surveillance of the lung is crucial for host defense.
- Understanding the roles of different immune cells in the lung is essential.
Purpose of the Study:
- To analyze and compare the contribution of monocytes to lung immune surveillance in the steady state.
- To differentiate monocytes from resident mononuclear phagocytes using transgenic reporters.
- To investigate the migratory properties and spatial organization of monocytes in the lung.
Main Methods:
- Utilized ECFP and EGFP transgenic reporters (Csf1r and Cx3cr1) to distinguish cell types.
- Employed functional imaging on explanted lungs to study cell migration.
- Analyzed the localization of monocytes within lung vasculature and alveolar interfaces.
Main Results:
- Monocytes were observed patrolling within lung vessels and at the lung capillary-alveoli interface.
- This positioning enables monocytes to capture particles from both vascular and airway sources.
- Monocytes demonstrated migratory activity without immediate differentiation into macrophages.
Conclusions:
- Monocytes actively participate in steady-state immune surveillance of the lung.
- Their role is complementary to that of resident macrophages and dendritic cells.
- Monocytes contribute to lung immunity through migration and particle capture, independent of immediate differentiation.
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