Functional aspects of mononuclear phagocyte involvement in lung inflammation.

The theme we have presented herein is that of the adaptability of the mononuclear phagocyte. This has been illustrated by discussing the mechanisms underlying the emigration of blood monocytes into peripheral tissues and organs under steady state and inflammatory conditions. Our basic tenet is that monocytes represent a relatively homogeneous cell population which migrates, either randomly or selectively, into a tissue and matures, following interaction with tissue components (be they normal or inflammatory), into macrophages characteristic of that tissue. Thus it is the interaction of a mononuclear phagocyte with an inflammatory stimulus that directs the phagocyte to mature into an inflammatory macrophage. Finally, we have also discussed how stimulus impingement on macrophages influences the products these cells secrete. We conclude that macrophages are essential to both the degradative and remodeling phases of an inflammatory response.