Alveolar macrophages and type I IFN in airway homeostasis and immunity

Globally, respiratory infections cause more than 4 million deaths per year, with influenza and tuberculosis (TB) in particular being major causes of mortality and morbidity. Although immune cell activation is critical for killing respiratory pathogens, this response must be tightly regulated to effectively control and eliminate invading microorganisms while minimizing immunopathology and maintaining pulmonary function. The distinct microenvironment of the lung is constantly patrolled by alveolar macrophages (M phi), which are essential for tissue homeostasis, early pathogen recognition, initiation of the local immune response, and resolution of inflammation. Here, we focus on recent advances that have provided insight into the relation between pulmonary M phi, type I interferon (IFN) signaling, and the delicate balance between protective and pathological immune responses in the lung.