Research progress of alveolar macrophages in pulmonary homeostasis and infections

Alveolar macrophages (AMs) are important immune cells in the lung.Different sources and polarization states make AMs play diverse functions in varying environment.Under physiological conditions, AMs are responsible for keeping lower levels of inflammation and maintaining homeostasis in the lung, promoting optimal gas exchange.They also mediate an immune response to invade microbes during infection and adjust their immune state in the later stage to reduce tissue damage and restore homeostasis, but may drive pathogen persistence.This review discusses the origin, polarization and functions of AMs in pulmonary homeostasis and infection, so as to provide new ideas for therapeutic strategy targeting at AMs. Key words: Macrophages, alveolar; Origin; Polarization; Pulmonary homeostasis; Pulmonary infection