The acute systemic inflammation associated with sepsis and chronic lung diseases such as cystic fibrosis can serve as a paradigm for studying how innate immune cells, particularly neutrophils, can shape the systemic and local immune response to infections. Pulmonary infections are a major cause of death worldwide, responsible for destabilizing chronic lung pathologies, sepsis and acute respiratory distress syndrome. They can affect immunocompetent hosts, patients with chronic respiratory diseases, or patients with systemic immune deficiency. Part of the team is focused on deciphering the role and functions of neutrophils in infectious and non-infectious pathological conditions. The other part currently focuses on host-pathogen interactions in severe acute infections (sepsis) and chronic pulmonary infections as encountered in COPD, bronchiectasis and cystic fibrosis. Our team is interested in the molecular mechanisms behind the unresolved neutrophil-dominated inflammation associated with chronic infection with Pseudomonas aeruginosa, a pathogen found notably in cystic fibrosis. In addition, our team revealed dendritic cell dysfunction and the contribution of neutrophils to lung injury in patients with severe SARS-CoV-2 pneumonia. This work has generated new concepts in the phenotypic and functional plasticity of immune cells, particularly neutrophils during acute respiratory distress syndrome.