The alveolar macrophage is the main resident natural immune cells in the lung,which plays an important role in the occurrence,development and complete resolution of acute lung injury.In the early stage,the resident alveolar macrophages recruit exudated macrophages and neutrophils by releasing chemokines and start inflammation progress.With the further development of inflammation,the regulation of alveolar macrophage inhibit the excessive activation of neutrophils and control inflammation progress.In the late stage,the alveolar macrophages undergo apoptosis during resolving inflammation,which affect the resolution and prognosis of acute lung injury.