Type 2 immune responses in endotoxemia-induced lung injury

Mayo Clinic Arizona, a nonprofit academic medical center and research institution, received a $486,109 Project Grant from the National Institute of Allergy and Infectious Diseases (NIAID) under the Allergy and Infectious Diseases Research program (CFDA 93.855). The award, effective July 1, 2025, through June 30, 2027, supports investigator-initiated biomedical research examining Type 2 immune responses in endotoxemia-induced lung injury. The research project addresses the critical clinical problem of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS), which represent leading causes of mortality in emergency departments and intensive care units.

The funded research investigates novel methods to amplify Type 2 immune responses of eosinophils in ALI/ARDS through two primary approaches: activation by IL-33 (interleukin-33) cytokine signaling and suppression of the IRF1 transcription factor. The research aims to define how eosinophils and innate lymphoid cells (ILC2s) contribute to injury repair and resolution. Preliminary evidence suggests that increased eosinophil numbers correlate with improved survival outcomes in certain ALI/ARDS patients, and that IL-33-activated eosinophils promote Type 2 effector functions critical to disease resolution. The project will generate fundamental scientific knowledge regarding immunological mechanisms underlying lung injury recovery, potentially informing future therapeutic interventions for this severe clinical condition.

Abstract

Acute lung injury (ALI)/acute respiratory distress (ARDS) is major cause of mortality in emergency rooms and intensive care units in hospitals. Identifying a role for eosinophils in ARDS has been limited, in part due to the technological difficulties in studying these cells, their association as destructive degranulating cells in asthma, and their low numbers in the lungs in some forms of ARDS. Rather, eosinophils are pleiotropic cells with complex immune activities in health and disease, where even small numbers of eosinophils may have a large impact on the immune responses in situ. In agreement with this, recent studies have found that an increase in eosinophil numbers in the lung correlated with survival in some patients with ALI/ARDS. In translational models of ALI/ARDS, lung eosinophils were necessary for reduced injury, improved resolution, and better survival. In particular, the type 2 immune responses of eosinophils were suggested to promote resolution of injury. In this proposal we will define and investigate two novel methods to amplify type 2 immune responses of eosinophils in ALI/ARDS to better understand how these cells may contribute to repair/resolution of injury. We hypothesize that increasing type 2 immune responses of eosinophils through activation by IL-33 or suppression of transcription factor IRF1 will result in reduced injury and increased resolution of ALI/ARDS. In models of ALI, increased IL-33 promoted recruitment and activation of eosinophils and group 2 innate lymphoid cells (ILC2S) that correlated with improved neutrophil resolution and survival. IL-33 binds the ST2 receptor on eosinophils and ILC2S and increases their type 2 effector functions. We recently identified IL- 33-activated eosinophils significantly promoted ILC2 type 2 effector functions in vitro and in vivo. We propose IL-33 signaling is critical for the eosinophil-ILC2 nexus that promotes type 2 responses, and enhancing this response in endotoxemia-induced ALI will be beneficial to resolution. In aim 1 we will test the role of IL-33 with eosinophil and ILC2-specific knockouts of ST2 to define their role in endotoxemia induced ALI. In aim 2, we will induce eosinophil type 2 immune responses by knocking out the transcription factor interferon regulatory factor 1 (IRF1) in eosinophils. We identified IRF1 as a novel major regulatory transcription factor of eosinophil immune phenotype in vivo and in vitro. IRF1 knockout eosinophils become type 2 immune cells in response to ifnγ. Our preliminary findings show IRF1 knockout mice have increased airway eosinophilia and eosinophil-specific IRF1 knockout mice have reduced neutrophilia during the resolution phase of endotoxin-induced ALI. We will complete studies with IRF1 knockout and eosinophil specific IRF1 knockout mice in endotoxemia-induced ALI. Importantly we will complete novel single cell analysis of the composition and phenotypes of lung immune cells using mass cytometry (CYTOF). These pathways are critical to define in order to identify the beneficial and/or negative consequences of eosinophil responses in ALI/ARDS.