The interdisciplinary research program will directly observe living cells of the immune system as they oxidize and lyse target cells. The oxidation and cytolysis of target cells have never previously been observed by optical microscopy. New biological and physical technologies now make this possible. Furthermore, the manner in which effector cells organize their plasma membranes to carry out these activities will be explored. Three model targets will be employed in these studies: 1) sheep erythrocytes, 2) 8E5 cells, which have been infected by human immunodeficiency virus, and 3) tumor cells. Neutrophil-mediated oxidation and cytolysis of IgG-opsonized erythrocytes will be observed by Soret band transmitted light microscopy and eosin Y labeling methods, respectively. The role of oxidative molecules will be studied using chronic granulomatous disease neutrophils. The cell surface distribution of neutrophil Fc receptors before, during, and after antibody- dependent cellular cytotoxicity will be determined. A similar series of experiments will be conducted on C3bi-opsonized erythrocytes and the complement receptor CR3. These results will be compared to the cytolytic mechanism(s) of lymphocytes. The neutrophil- and macrophage-mediated oxidation of 8E5 and tumor cells will be studied. The cytosol of nucleated target cells will be labeled with fluorescent compounds that are sensitive to oxidative conditions. The properties of effector cell surface Fc receptors during target cell oxidation will be studied during antibody-dependent cellular cytotoxicity. The oxidation of tumor targets during antibody-independent cytotoxicity will also be studied.