ABSTRACT
BACKGROUND: Exaggerated neutrophil-dominated inflammation underlies progressive cystic fibrosis (CF) lung disease. Older studies reported a defective respiratory burst in CF, but more recent studies suggest neutrophil function is normal. METHODS: We measured the amount and rate of reactive oxygen species (ROS) during PMA-stimulated respiratory burst activity in children [70 CF, 13 disease controls, 19 health controls] and adults [31 CF, 14 health controls] in neutrophils harvested from peripheral blood. Blood was collected from participants with CF when clinically stable (60 children, 9 adults) and on hospital admission (38 children, 24 adults) and discharge (18 children, 21 adults) for acute pulmonary exacerbations. RESULTS: When clinically stable, children with CF had lower ROS production [median 318,633, 25% 136,810 - 75% 569,523 RLU] than disease controls [median 599,459, 25% 425,566 - 75% 730,527 RLU] and healthy controls [median 534,073, 25% 334,057 - 75% 738,593 RLU] (p = 0.008). The rate of ROS production was also lower (p = 0.029). In neither children nor adults with CF did ROS production increase on hospital admission for acute pulmonary exacerbation, nor fall prior to discharge. There were no associations between ROS production and high-sensitivity C-reactive protein (indicating systemic inflammation) in either children or adults with CF. CONCLUSIONS: Our data do not support a role for exaggerated respiratory burst activity contributing to the exaggerated neutrophil-dominated inflammation seen with CF lung disease.
Subject(s)
Cystic Fibrosis , Adult , Child , Humans , Inflammation/metabolism , Neutrophils/metabolism , Reactive Oxygen Species/metabolism , Respiratory BurstABSTRACT
Rationale: A subset of infants are hypersusceptible to severe/acute viral bronchiolitis (AVB), for reasons incompletely understood. Objectives: To characterize the cellular/molecular mechanisms underlying infant AVB in circulating cells/local airway tissues. Methods: Peripheral blood mononuclear cells and nasal scrapings were obtained from infants (<18 mo) and children (≥18 mo to 5 yr) during AVB and after convalescence. Immune response patterns were profiled by multiplex analysis of plasma cytokines, flow cytometry, and transcriptomics (RNA-Seq). Molecular profiling of group-level data used a combination of upstream regulator and coexpression network analysis, followed by individual subject-level data analysis using personalized N-of-1-pathways methodology. Measurements and Main Results: Group-level analyses demonstrated that infant peripheral blood mononuclear cell responses were dominated by monocyte-associated hyperupregulated type 1 IFN signaling/proinflammatory pathways (drivers: TNF [tumor necrosis factor], IL-6, TREM1 [triggering receptor expressed on myeloid cells 1], and IL-1B), versus a combination of inflammation (PTGER2 [prostaglandin E receptor 2] and IL-6) plus growth/repair/remodeling pathways (ERBB2 [erbb-b2 receptor tyrosine kinase 2], TGFB1 [transforming growth factor-ß1], AREG [amphiregulin], and HGF [hepatocyte growth factor]) coupled with T-helper cell type 2 and natural killer cell signaling in children. Age-related differences were not attributable to differential steroid usage or variations in underlying viral pathogens. Nasal mucosal responses were comparable qualitatively in infants/children, dominated by IFN types 1-3, but the magnitude of upregulation was higher in infants (range, 6- to 48-fold) than children (5- to 17-fold). N-of-1-pathways analysis confirmed differential upregulation of innate immunity in infants and natural killer cell networks in children, and additionally demonstrated covert AVB response subphenotypes that were independent of chronologic age. Conclusions: Dysregulated expression of IFN-dependent pathways after respiratory viral infections is a defining immunophenotypic feature of AVB-susceptible infants and a subset of children. Susceptible subjects seem to represent a discrete subgroup who cluster based on (slow) kinetics of postnatal maturation of innate immune competence.
