PROJECT SUMMARY/ABSTRACT The acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure in the intensive care unit due to overwhelming inflammation in the lung without effective disease modifying treatments. Two sub- phenotypes of ARDS have been identified based on clinical parameters and biomarkers. Compared to hypo- inflammatory ARDS, hyper-inflammatory ARDS is characterized by shock, acidosis, and elevated inflammatory biomarkers. Patients with hyper-inflammatory ARDS have a higher mortality and may respond differentially to treatment. The overarching goal of this training grant proposal is to utilize cutting edge immunology techniques to dissect the immune mechanisms underlying ARDS development and the differentiation between the two sub-phenotypes. In our preliminary data, we identified reduced expression of tristetraprolin (TTP), a negative regulator of cytokine production, in natural killer (NK) cells of patients with ARDS. In Aim 1, we will investigate the mechanisms by which TTP regulates NK cell activation. Additionally, we will use PrimeFlow, a novel flow cytometry-based mRNA quantification technique, to determine if NK cells from patients with ARDS are refractory to negative feedback by inflammatory cytokines due to reduced TTP expression. In Aim 2, we will focus on discovery of immune mechanisms that differentiate hyper- and hypo-inflammatory ARDS. We have found increased frequency of circulating inflammatory non-classical CD14-CD16+ monocytes in hyper- inflammatory ARDS when compared to hypo-inflammatory ARDS patients. We propose using cellular indexing of transcriptomes and epitopes with sequencing (CITE-seq) to investigate signaling pathways at the single cell level in monocytes that differentiate hyper- and hypo-inflammatory ARDS. CITE-seq references single cell RNA sequencing transcriptomic data to surface expression of proteins thereby correlating the transcriptome with flow cytometric surface phenotypes. Together, aims 1 and 2 will test our overall hypotheses that NK cells in ARDS patients are resistant to negative feedback due to reduced TTP expression, and persistent activation of CD16+ non-classical monocytes determines the hyper-inflammatory phenotype of ARDS. Further delineation of immune mechanisms in the development and maintenance of ARDS will advance our understanding of its pathogenesis and identify potential therapeutic targets to modify the disease course of ARDS. The research proposed within this training fellowship will be undertaken at the University of Pittsburgh through a collaborative training environment between the Division of Pulmonary, Allergy and Critical Care Medicine and Department of Immunology to develop research skills in translational human and computational systems immunology. Formal training in the responsible conduct of research and scientific rigor are included in this training proposal, and career development through presentation of research, publication and a multi-di...