W219 - Alveolar Macrophage Subsets Defined by Single Cell RNA Sequencing Associate with Mortality in Acute Respiratory Failure

Eric Morrell – Pulmonary and Critical Care Medicine – University of Washington; Sarah Holton – Translational Immunology – Benaroya Research Institute; Matthew Lawrance, MSc – Benaroya Research Institute; Zoie Franklin, B.S. – Benaroya Research Institute; Mallorie Mitchem – Benaroya Research Institute; Ashley Garay – Pulmonary and Critical Care Medicine – University of Washington; Elizabeth Barnes, B.S. – Pulmonary and Critical Care Medicine – University of Washington; Ted Liu – Pulmonary and Critical Care Medicine – University of Washington; Ithan Peltan – Intermountain Healthcare; Angela Rogers – Stanford University; Steven Ziegler – Benaroya Research Institute; Mark Wurfel – Pulmonary and Critical Care Medicine – University of Washington; Carmen Mikacenic – Benaroya Research Institute

Abstract Text: Alveolar macrophages are highly plastic and are the most abundant cell in the homeostatic human lung. The transcriptional and phenotypic characteristics of alveolar monocyte and macrophage (mono-AM) subsets in acute respiratory failure are poorly understood. In this study, we wanted to identify novel mono-AM subsets in patients with acute respiratory failure, examine changes over time, and test for associations between subsets and mortality. From a cohort of patients with non-infectious lung injury on mechanical ventilation (n=8), we performed bronchoalveolar lavage (BAL) and collected peripheral blood within 96 hours of hospital admission and 72 hours later. We utilized CITE-seq (scRNA-seq and cell surface proteins) to establish mono-AM subsets. Six AM subsets and 2 monocyte subsets were identified in BAL. In paired peripheral blood, we identified monocyte subpopulations with similar gene expression programs to those in BAL. The proportion of AM subsets with cholesterol processing and complement gene expression profiles increased over time. Cell-surface proteins including CD71, CD163, and CD86 distinguished AM transcriptional subsets. In a second cohort of mechanically ventilated patients (n=51), we used flow cytometry to identify mono-AM subsets defined by our CITE-seq. We found a higher proportion of the alveolar CD163/LGMN subset (CD71-CD163+) was associated with mortality (p < 0.01). In this study of patients with non-infectious lung injury, we identified novel alveolar mono-AM populations as well as previously described subsets in COVID-19. The proportion of mono-AM subsets rapidly changes and can be identified by cell surface proteins. This facilitated our identification of associations between CD163/LGMN AMs and mortality.