An extraordinary development of the knowledge, concepts and biomedical applications has occurred during the past two decades in the biological sciences, including the Reticuloendothelial Sys tem (RES). For example, it is now widely recognized that distinct classes of cells are involved in the recognition of "exogenous" invaders of the body such as microorg~nisms and other foreign an tigens, as well as of "endogenous" parasites represented by trans formed neoplastic cells and altered "self" antigens. Prominent among cell populations involved in such recognition of antigens and subsequent immune responses are those constituting the RES. In recent years, there has been much discussion and indeed contro versy as to what constitutes such a system and even whether the term "RES" is appropriate. Some investigators feel that the phago cytes are the most important cells of the RES as they playa major role in the defense mechanism of the host. Mononuclear phagocytes include tissue macrophages as well as circulating monocytes and their precursors. Although phagocytosis is a major functional ac tivity, it is only one of their several functions. The important role of phagocytes and other mononuclear cells in antibody forma tion, cell-mediated immunity, specific and non-specific resistance to microorganisms and tumor cells, as well as homeostatic adjust ments in general has become the focus of attention for many inves tigators.

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of Part A.- Section 1 Morphology and Surface Properties of Macrophages.- The RES and the Mononuclear Phagocyte System.- Morphology and Kinetics of Lymphocytes.- Differences Between Monocyte-Derived and Tissue Macrophages.- Cellular Basis for the Generation of B-Cell Diversity.- Antigenic Differences Between Rat Alveolar and Peritoneal Macrophages.- A Macrophage Cell Surface Antigen.- Section 2 Ontogeny and Development of RE Cells.- Origin, Ontogeny and Kinetics of Mononuclear Phagocytes.- Germinal Centers and Their Role in Immune Responses.- Distribution of HL-A Antigens and ABO Blood Groups in Pre-Columbian Mummies.- Immunological Reconstitution of Neonatally Thymectomized Rats Following Implantation of Thymic Epithelial Cells.- Section 3 Biochemistry and Physiology of the RES.- Biochemical Aspects of the Function of the Reticulo-Endothelial System.- Cyclic Nucleotide Metabolism of Reticuloendothelial Cells.- Nitroblue Tetrazolium Reduction by Human Macrophages: Studies in Chronic Granulomatous Disease.- The NADPH Oxidase Activity of Polymorphonuclear Neutrophilic Leukocytes Revisited.- Chemotaxis of Polymorphonuclear Neutrophilic Leukocytes by Mannan-Enriched Preparations of Candida albicans.- Iron and the Reticuloendothelial System.- Section 4 The Phagocytic Event.- Chlorination, Decarboxylation and Bactericical Activity Mediated by the MPO-H2O2-Cl- System.- The Mechanism of Control of Phagocytic Metabolism.- Genetic Regulation of Macrophage Functions.- Electron Microscopic Cytochemical Localization of Intravenously Injected Liposome-Encapsulated Horseradish Peroxidase in Rat Liver Cells.- Phagocytosis and Intralysosomal Digestion of Subcellular Organelles by Kupffer Cells of Rat Liver.- The Role of Phagocytosis in the Production of Endogenous Pyrogen by Polymorphonuclear Leukocytes.- Antiphagocytic Activity of the Cell Wall Polysaccharide of Escherichia coli.- The Reticuloendothelial System (RES) in Experimental Amebic Meningoencephalitis.- Section 5 Factors Affecting RE Function.- The Selection and Design of Lysosomotropic Drugs.- Surface Receptors in B Lymphocyte Activation by Antigens.- Mechanisms of Lymphocyte Activation: Effect of Ligand Concentration and Induction Time.- Complement Independent Lipopolysaccharide (LPS) Induced Hypotension and Disseminated Intravascular Coagulation: A Correlation of LPS Structure with In vivo and In vitro Biological Activities.- Potentiated Lysosomal Enzyme, Bacteriostatic and Bactericidal Activities of Peritoneal Macrophages of Mice Treated with the MER Fraction of Tubercle Bacilli.- Adjuvant Effect of Listeria Cell Wall Fraction.- The Present View of RES and Shock.- Trauma Induced Histamine Synthesis and RES Activity.- Workshops.- RES Biochemistry and Physiology.- RES Pharmacology.- List of Participants.