Fig. 5.

Macrophages in homeostasis.

This figure portrays all the processes involved in cessation and repair of alveolar inflammation after acute inflammatory lung injury Homeostasis is a timely coordinated, active process in which alveolar macrophages are directly or indirectly involved. These processes include blockage of granulocyte (PMN) and monocyte influx from the circulation, phagocytosis of apoptotic polymorphonuclear neutrophils or parenchymal cells, initiation of angiogenesis, repair of the endo-and epithelial barrier by junctional sealing, clearance of alveolar edema, proliferation/differentiation of epithelial progenitor cells including type II alveolar epithelial cells (AEC), removal of fibrin and protein rich edema fluid. These processes are well synchronized and are critical for healthy tissue homeostasis.