The overall purpose of these studies is to increase understanding of the structure and function of human phagocytic cells in their role as the primary defense against infection. The main goal of the proposed research is to study the antigenic components of the neutrophil membrane. Methods of isolating neutrophil membranes utilizing a two phase polymer centrifugation system or by isolating neutrophil membrane adherent to petri dishes have been developed. It is planned to characterize the membrane proteins utilizing two dimensional systems of polyacrylamide gel electrophoresis. The proteins or their antigenic domains will be defined by coomasie blue or PAS staining, radioisotope labeling, lectin binding, or binding of anti-neutrophil antibodies isolated from both animals and from patients with antineutrophil antibodies. Ferritin-labelled lectins or antibodies will be used to characterize the distribution of protein antigens on the outer and inner surface of neutrophil membranes. These studies should define the major protein antigens of the human blood neutrophil and identify which ones are involved in the binding of neutrophil specific antibodies produced in patients with autoimmune neutropenias.