Type III interferon drives pathogenicity to Staphylococcus aureus via the airway epithelium

Abstract

Type III interferon signaling contributes to the pathogenesis of the important human pathogen Staphylococcus aureus in the airway. Little is known of the cellular factors important in this response. Using Ifnl2-green fluorescent protein reporter mice combined with flow cytometry and cellular depletion strategies, we demonstrate that the alveolar macrophage is the primary producer of interferon lambda (IFN-λ) in response to S. aureus in the airway. Bone marrow chimeras showed reduced bacterial burden in IFN-λ receptor (IFNLR1)-deficient recipient mice, indicative that non-hematopoietic cells were important for pathogenesis, in addition to significant reductions in pulmonary inflammation. These observations were confirmed through the use of an airway epithelial-specific IFNLR knockout mouse. Our data suggest that upon entry to the airway, S. aureus activates alveolar macrophages to produce type III IFN that is subsequently sensed by the airway epithelium. Future steps will determine how signaling from the epithelium then exerts its influence on bacterial clearance. These results highlight the important, yet sometimes detrimental, role of type III IFN signaling during infection and the impact the airway epithelium plays during host–pathogen interactions.