A high dimensionality approach reveals immunopathogenic responses driving severe pediatric acute respiratory distress syndrome.

Mechanisms underlying paediatric acute respiratory distress syndrome (PARDS) remain poorly understood, limiting advances in diagnosis and treatment. To address this, we conduct a high-dimensional, multi-omics analysis of paired pulmonary and blood samples from children with PARDS and age-matched controls. Our approach includes transcriptomics, proteomics, flow and mass cytometry, and single-cell RNA sequencing, with further validation using cytokine assays and in vitro models. Severe PARDS is characterised by three convergent immune abnormalities; Pulmonary CD8 + T cells display an interferon-driven cytotoxic profile, with exhaustion and apoptosis genes; Pulmonary T cells and myeloid cells exhibit strong interferon-stimulated gene expression; Distinct macrophage subsets show high interferon but suppressed IL-1 pathway genes, associated with impaired leukocyte chemotaxis, phagocytosis, and M1-polarization. This is mirrored by reduced pulmonary IL-1α/β and elevated IFN-γ. The systemic IL-1 signature is similarly dampened, while interferon responses are compartmentalised to the lung. Using an in vitro model, IFN-γ priming is shown to suppress TLR7-induced IL-1 β production through transcriptional inhibition of downstream inflammatory pathways, recapitulating the immune signature observed in patients. Our results reveal interferon-driven immune dysregulation and IL-1 suppression as central features of severe PARDS, highlighting parallels and differences from adult ARDS and underscoring the need for paediatric-specific therapeutic strategies.