We propose to utilize a newly developed microdroplet dye exclusion cytotoxicity test using cytochalasin-B treated granulocytes to investigate (Gr) antigen antibody interaction. Objectives are outlined as follows: First, define antigens and patterns of inheritence. Second, elucidate the immunization pattern in granulocyte transfusion recipients and study cases which may be the result of autoimmune or isoimmune mechanisms. Third, determine the in vitro effect of antibody on granulocyte function and the in vivo effect on cell survival. Fourth, determine the distribution of Gr antigen in tissue. Fifth, determine immunoglobulin class, quantitate antigen density and analyze the interaction of antigen and antibody. In screening studies monospecific (determined by absorption) sera will be collected. Lymphocyte cytotoxicity and leukagglutinating activity will also be ascertained. Analysis (2 times 2 contingency tables) will determine positive and negative associations. A genetic hypothesis will be formulated and gene frequencies calculated. The theory will be tested (chi2 goodness of fit test and family studies). Tests of the in vitro effect of antibody on granulocyte function will include adherence to nylon fibers, chemotaxis, phagocytosis, degranulation, lactate production, oxygen uptake and superoxide formation. Survival studies using radiolabelled granulocytes will elucidate the in vivo effect of cytotoxins. Tissue distribution will be ascertained by absorption in some cases and by cytotoxicity testing and absorption in other cases. Cytotoxins will be fractionated (DEAE cellulose and sephadex G-200 chromatography) concentrated (Aminco) and tested for activity. In addition fractions will be tested after immunoabsorption with monospecific antisera. Analysis of the interaction between antigen and antibody will be studied by radiolabelling (125I) methods. Antibody will be purified by absorption and elution, association and dissociation kinetics measured and equilibrium experiments plotted to ascertain estimates of the equilibrium constant and antigen density.