We shall continue to study the destruction of blood cells, both normal and neoplastic, by immunological mechanisms. We shall investigate the nature of the membrane defect in paroxysmal nocturnal hemoglobinuria, using techniques of membrane protein purification. We shall compare the abnormalities seen in these disorders in which there appears to be a defect in the resistance to the lytic action of complement or in the expression of the antigens of the major red cell membrane glycoprotein. We shall continue to study the nature of the antibody in immune thrombocytopenia and relate this to the clinical stats associated with thrombocytopenia, including lymphoma and CLL. The ability of these antibodies to fix complement, the nature of their immunoglobin typing, and the effects of therapeutic measures on the qualitative and quantitative aspects of these antibodies will be investigated. We will continue our microcinematographic and electron microscopic studies of the process of red cell-phagocyte interaction, using available quantitative and qualitative techniques better to define the antibodies involved. We will continue our studies on the phagocytosis of red cells by lymphocytes.