Microenvironmental impact on lung cell homeostasis and immunity during infection.

The lung is a vital organ devoted mainly to gas exchange with an external environment that may be contaminated with various life-threatening pathogens and inert particles. Lung immunity must be permanently balanced between costimulatory and coinhibitory signals, thus controlling potential pathogens while avoiding detrimental inflammation. The lung harbors macrophages and dendritic cells (myeloid and plasmacytoid), which orchestrate the primary defense against microbial invaders. During an infection involving host-microbial synapses, microbes either escape by using host cell physiology or are eliminated by a robust immune response. We thus focus on the dynamics of such cellular interactions within the lung and stress the critical role played by airway epithelial cells in modulating immunity.