Macrophage PD-1 associates with neutrophilia and reduced bacterial killing in early cystic fibrosis airway disease

Macrophages are the major resident immune cells in human airways coordinating responses to infection and injury. In cystic fibrosis, neutrophils are recruited to the airways shortly after birth, and actively exocytose damaging enzymes prior to chronic infection, suggesting a potential defect in macrophage immunomodulatory function.