Regional macrophage activation after injury and the compartmentalization of inflammation in trauma

The mononuclear phagocyte or macrophage (M phi) system is an important early participant in the human immune response to injury. M phi are uniquely able to transduce a broad variety of nonspecific physical and chemical stimuli generated in traumatized tissues as well as specific immune signals (such as cytokines) into coherent response patterns. Thus, M phi occupy a central position in the overall response in that they can initiate specific, cognate immune responses to injury. M phi are both responsive to cytokine signals and key inducers of cytokine-mediated patterns of response in other cells. Not only do the responses of M phi in different diseases states very widely, but these responses may vary from location to location and over time in the same organism. This article examines the role of M phi in the response to injury, focusing on local activities and the hypothesis that local M phi response patterns (and their pathologic loss) may be involved in the generation of immune-mediated organ injury distant from sites of direct trauma.