Role of toxic oxygen products from phagocytic cells in tissue injury

The generation of toxic oxygen products from activated phagocytic cells represents an important pathogenic mechanism in tissue damage associated with inflammatory reactions that are characterized by the involvement of neutrophils or other phagocytic cells. The production of these toxic products from activated phagocytic cells is related to receptor activation on the surface of the cells. Most emphasis has been placed on studies in the lung where the production of these toxic metabolites by phagocytic cells, either in the vasculature or in the airway compartment of the lungs, has been demonstrated to result in endothelial cell injury or damage and destruction of alveolar lining cells. In some cases these reactions are progressive, resulting in parenchymal collapse and fibrosis. Naturally occurring protective factors have been demonstrated both within cells and in the plasma and interstitial fluid compartments. Although there is increasing evidence that in the shock syndrome complement activation products and toxic oxygen metabolites from activated leukocytes play important roles, the most direct evidence for related mechanisms comes in detailed studies of immune complex induced injury where a role for both O-2 and H2O2 has been clearly demonstrated. These facts indicate that toxic oxygen metabolites from activated phagocytic cells play important roles in a variety of pathological situations, and have provided new insights into intervention therapy.