Infection of the airways is a major cause of death worldwide and a persistent problem in critical care medicine. Mortality from airway infection is on the rise and thus there is an urgent need to develop alternative treatments. Innate response activator (IRA) B cells are a unique B cell population we recently discovered that protects against microbial sepsis. In a mouse abdominal sepsis model, peritoneal B1a B cells recognize bacteria with pattern recognition receptors, migrate to the spleen, differentiate to IRA B cells, and protect against overwhelming infection by mechanisms that involve the cytokine and growth factor GM-CS. IRA B cells, which we also identified in humans, are vital to how the host clears bacteria. We have now shown in preliminary experiments that B1a B cells and IRA B cells also reside in the pleural cavity. Mice lacking IRA B cells rapidly succumb to bacterial airway infection, fail to accumulate IgM-producing cells in the lungs, and fail to generate secretory IgM. Moreover, the pleural cavity is the source of IgMhigh B cells that accumulate in the lungs, whereas injection of pleural cavity IRA B cell precursors to the pleura of IRA B cell knockouts restores IgM responses and protects against bacterial infection. Here we will test the hypothesis that pleural cavity-derived IRA B cells control the generation and accumulation of natural antibody producing cells in the lung. IRA B cells, we propose, are essential coordinators of immune defense and protect against airway infection. The project is important because it is based on a strong phenotype and has clear translational potential and it is innovative because it explores the biology of a newly- discovered cell, identifies a previously unknown GM-CSF-IgM axis, and identifies the pleural cavity as an important hub for immune cells.

Public Health Relevance

Airway infection is a very serious condition that has a high mortality and is on the rise. Innate response activator (IRA) B cells are a newly discovered population of cells that protect against bacterial infection. IRA B cells develop in the pleural space, a region surrounding the lung that helps in respiration but that has unknown function in immunity. Experiments proposed in this grant will aim to unravel the role of pleural space IRA B cells in airway infection and will test whether IRA B cells can be used therapeutically.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
High Priority, Short Term Project Award (R56)
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Innate Immunity and Inflammation Study Section (III)
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Davidson, Wendy F
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Massachusetts General Hospital
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Theurl, Igor; Hilgendorf, Ingo; Nairz, Manfred et al. (2016) On-demand erythrocyte disposal and iron recycling requires transient macrophages in the liver. Nat Med 22:945-51
Nahrendorf, Matthias; Swirski, Filip K (2016) Innate immune cells in ischaemic heart disease: does myocardial infarction beget myocardial infarction? Eur Heart J 37:868-72
Chousterman, Benjamin G; Swirski, Filip K (2015) Innate response activator B cells: origins and functions. Int Immunol 27:537-41
Weber, Georg F; Chousterman, Benjamin G; He, Shun et al. (2015) Interleukin-3 amplifies acute inflammation and is a potential therapeutic target in sepsis. Science 347:1260-5
He, Shun; Chousterman, Benjamin G; Fenn, Ashley et al. (2015) Lp-PLA2 Antagonizes Left Ventricular Healing After Myocardial Infarction by Impairing the Appearance of Reparative Macrophages. Circ Heart Fail 8:980-7
Nahrendorf, Matthias; Swirski, Filip K (2015) Lifestyle effects on hematopoiesis and atherosclerosis. Circ Res 116:884-94
Weber, Georg F; Chousterman, Benjamin G; Hilgendorf, Ingo et al. (2014) Pleural innate response activator B cells protect against pneumonia via a GM-CSF-IgM axis. J Exp Med 211:1243-56
Pittet, Mikael J; Nahrendorf, Matthias; Swirski, Filip K (2014) The journey from stem cell to macrophage. Ann N Y Acad Sci 1319:1-18
Hilgendorf, Ingo; Gerhardt, Louisa M S; Tan, Timothy C et al. (2014) Ly-6Chigh monocytes depend on Nr4a1 to balance both inflammatory and reparative phases in the infarcted myocardium. Circ Res 114:1611-22
Swirski, Filip K; Nahrendorf, Matthias (2014) Do vascular smooth muscle cells differentiate to macrophages in atherosclerotic lesions? Circ Res 115:605-6

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