Table 1. Summary of factors contributing to infection and pulmonary decline in cystic fibrosis
Lung environment
    Defective cilia function
    Increased mucus viscosity, hypoxia
    Free nutrients: amino acids, iron
    Damage to lung architecture: TGF-β, matrix metalloproteases, neutrophil elastase, oxidant/antioxidant imbalance
    Altered pH
Immune dysfunction
    Defective and/or decreased antimicrobials: lysozyme, lactoferrin, β-defensins, pentraxin-3, thiocyanate, nitric oxide, surfactant protein D
    Th2 and Th17 responses
    Ineffective cellular mediators: neutrophil accumulation and dysfunction
Microbial factors
    Changes in virulence: lipid A structure, flagellin expression, loss of quorum sensing, acquisition of a persistent phenotype and hypermutation
    Biofilm formation
    Polymicrobial interaction and secondary infection
    Direct downregulation of antimicrobial pathways: vitamin D receptor downregulation by Aspergillus
  • TGF: transforming growth factor; Th: T-helper cell.