The production of alveolar macrophage-derived growth-regulating proteins in response to lung injury.

Tissue injury elicits an inflammatory response, one element of which is the activation of the local macrophage population. Macrophages are recognized as the source of multiple growth-regulating proteins, and are thus thought to play an important role in wound healing. Injury to the lung by exposure to oxidant gases, particulates, chemicals or drugs is often followed by replication of the cells of the alveoli. The growth-regulating proteins released by alveolar macrophages (AM) may be one mechanism which controls the proliferation of these cells. This article describes the AM growth factors, the cell types which they affect, and the injuries known to cause their release. In view of the multiplicity and overlapping functions of the macrophage growth factors, potential mechanisms which might regulate the growth response of the surrounding cells are also considered.