The goals of the proposed program are a comprehensive analysis of the cellular and biochemical mechanisms of the conversion of oxygen to superoxide (02.-) and other high reactive radicals by human PMN leukocytes, an examination of the activation and modulation of these oxidative pathways by highly purified or synthetic mediators of the leukocyte component of immunological responses, and the definition of the roles of the oxygen metabolites of PMN leukocytes in host defense and in the tissue destruction associated with some inflammatory reactions. The NADPH-dependent (02.-) generating activity of human PMN leukocytes will be purified to a state of homogeneity in order to permit studies of the enzymatic mechanisms of (02.-) formation. A unique cytochrome b of PMN leukocytes, that has been implicated in (02.-) generation, will be isolated to elucidate its role as a co-factor. Antibodies will be prepared to both the highly purified NADPH-dependent (02.-) generating oxidase and the b type cytochrome to assess the functional role of each component, the process of activation, and the subcellular localization of the (02.-) generating activity in intact PMN leukocytes. Biochemical and immunochemical techniques will be applied to the identification of distinct deficiencies in the oxidative pathways of PMN leukocytes which fail to exhibit a respiratory burst of normal magnitude. As autoinactivation of the NADPH-oxidase of human PMN leukocytes is a mechanism for the control of the production of (02.-), one facet of the program will consist of a biochemical analysis of the inactivation process. Since the interaction of human PMN leukocytes with defined immunological mediators of cellular function enhances the production of (02.-), the biochemical sequence that links specific receptors for the mediators to oxygen metabolism will be examined utilizing several classes of agonists and inhibitors.