Session 1 Ontogeny of Lymphoid Cells.- Differentiation and Ontogeny of Lymphoid Cells.- The Ontogeny of Bursa- and Thymus-Specific Cell Surface Antigens in the Chicken.- IgA Surface Determinants on Cells from the Chicken Embryo.- Contribution of the Bursa of Fabricius to the Maturation of the B Cell System in Chickens.- Bursa of Fabricius: Uptake of Radioactive Particles and Radiotoxic “Sealing” of Bursal Follicles.- The Need for Transcription and Translation for Differentiation of Bone Marrow Cells by Thymic Factors in Man.- Immunological Potential of Yolk Sac Cells.- Ontogeny of T Lymphocytes Studied in Athymic and Foetal Mice.- Ontogeny of T Cell Function in the Fetal Lamb.- Involvement of Cells with ‘B’ Properties in Development of T Helpers.- Studies on the Development of Immunity: General Considerations.- Session 2 Surface Properties and Activation of Lymphoid Cells.- Surface Properties of Lymphoid Cells: Introduction.- Is a Specialized Stimulator Cell Required for the Induction of Allograft Immunity?.- Cell Selection in the Thymus of Mice Treated with Escherichiacoli lipopolysaccharide (LPS).- Clonal Expansion and Thymus Dependence. Microculture Experiments with TNP-Lipopolysaccharide.- Cellular Events Involved in the True Primary Immune Response of Splenocytes in Vitro.- Nonspecific Esterase Activity in T Cells.- Thymocyte Subpopulations as Stimulators in the Mixed Lymphocyte Reaction.- Clonal Proliferation of Human Stimulated Lymphocytes on Agar Culture.- Spontaneous and Induced Changes in Thymus Pattern.- Thymocyte Maturation in AKR Leukemia.- Lymphocytes and Hemopoietic Bone Marrow Cells: Antigenic Relationships between these Cells and Lymphatic Tissue Repopulation from Stem Cells.- Demonstration of Two Distinct Macrophage Specific Antigenic Determinants in Rats.- Surface Properties of Lymphoid Cells: Summing up.- Session 3 Homing of Cells and Inductive Effects of Microenvironment and of Humoral Factors.- Microenvironment to a Lymphoid Cell is Nothing More Than Interaction with its Neighbours.- Scanning Electron Microscopy of B- and T-Cells in Peripheral Lymphoid Organs of the Mouse.- Human Lymphatic Microecology: Specificity, Characterization and Ontogeny of Different Reticulum Cells in the B Cell and T Cell Regions.- ‘Hyperlymphoid’ mice.- The Role of the Afferent Lymph in the Induction of Contact Sensitivity.- Studies on the Effect of Environment on the GVH Reactivity of Recirculating Lymphocytes.- The Recovery of the BCell Compartment in Lethally Irradiated and Reconstituted Mice.- Regulation of Thymic Lymphopoiesis in Vitro.- Isolation and Partial Chemical Characterization of THF, a Thymus Hormone Involved in Immune Maturation of Lymphoid Cells.- Regulation of Immune Balance by Thymosin: Potential Role in the Development of Suppressor T Cells.- Lymphoid Tissue Architecture. III. Germinal Centers, T Cells, and Thymus-Dependent vs. Thymus- Independent Antigens.- Summary and Afterthoughts on Session 3: Homing of Cells and Inductive Effects of Microenvironment and of Humoral Factors.- Session 4 Cell Interactions in Immune Responses.- Cell Interactions in Immune Responses: Role of T Lymphocytes.- Induction of Hapten Recognizing Helper Function by Heavily Trinitrophenylated Sheep Erythrocytes.- In Vitro Proliferative Reactions by Lymphocytes from Both Responder and ‘Low’ Responder Mice to (T,G)-A--L.- Effect of Interaction between Hapten-Specific Cells Preselected for Different Receptor Affinities and Carrier-Primed Cells on Antibody Avidity.- Cell Interaction in B/W Mice: A Reversible Defect at the T Cell Level.- T Cell Dependency of the Response to PVP is Dependent on Maturity of B Cells.- Differentiation of Cytotoxic T Lymphocytes Enhanced by T Cell Factors Produced during Mixed Lymphocyte Interactions.- Enhancing Effect of Radioresistant Spleen Cells on the Primary Immune Response against Sheep RBC by Mouse Spleen Cells in Vitro.- Effector Cell Requirements for Antibody-Dependent and Mitogen-Indueed Cytotoxicity.- Recruitment of Effector Lymphocytes by Initiator Lymphocytes: Recruited Lymphocytes are Immunospecific.- Histophysiology of the Helper T Cell System in Rabbits.- Interference of Cyclophosphamide with the Development of T Helper Activity in Rabbits.- Enhanced in Vitro Immunogenicity of H-2 Antigens in the Presence of la Antigens.- Cooperation is the Thing.- Session 5 Lymphoid Cell Receptors And Antigen Recognition.- Lymphoid Cell Receptors and Antigen Recognition.- Patterned Antigen-Binding Cells of Multiple Specificity.- Evidence for Two Antibody Molecules of Different Specificity Secreted by Bispecific Mouse Spleen PFC Micromanipulated in Vitro.- Early Events in the Generation of Antigen-Specific Cytotoxicity in MLC.- A Study of the Immunological Function of Fc Receptor-Bearing Cells among Activated Thymocytes.- Relation of Antigen-Binding Cells to Immunological Memory.- The Detection of IgD and IgM on Murine B-Lymphocytes in Conditions where no Ig can be found on T Lymphocytes.- The Influence of “I” Region Antibodies on Transplants.- Virus-Immune Cytotoxic T Cells are Sensitized to by Virus Specifically Altered Structures Coded for in H-2K or H-2D: A Biological Role for Major Histocompatibility Antigens.- Restriction by H-2 Gene Complex of the Transfer of Delayed Type Hypersensitivity in Mice.- Characterization and Specificity of a T Cell Cooperative Factor.- Rat Anti-Lymphocyte Alloantibodies Block Con A-Stimulation of T Lymphocytes: Inhibition of a Polyclonally Specific T Cell Reaction.- Recognition of Antigen by B and T Lymphocytes.- Session 6 Tumor Immunology: Interactions Between Lymphocytes, Antibodies and Neoplastic Cells.- Host Protection by the Antibody-Forming System in Malignancy.- Tumour Resistance of Tetraparental AKR?CBA Chimaeras.- Low Numbers of Tumor Cells Suppress the Host Immune System.- Studies on Effector Cell—Target Cell Interactions in Vitro by Means of the Quantitative Immunoadherence Technique.- Immunologic Responses of the Autochthonous Host against Tumors Induced by Ultraviolet Light.- The in Vivo Coating of Tumor Cells by Potentially Cytotoxic Antitumor Antibodies.- Modulation of the Immune Response in Vitro and in Vivo by Splenocytes from Tumor-Bearing Mice.- Divalent Cation Requirements as a Tool for the Study of Cell-Mediated Cytotoxicity Systems.- Macrophage Killing Capacity. Aspects of Mechanism.- A New T Cell Neoplasm Expressing Surface Anti-DNP Activity, Developed from the Thymus of Mice Bearing MOPC-315 Plasma Cell Tumors.- Lymphocyte—Target Cell Conjugation: Membrane Receptors for Alloantigens.- Observations in Vitro Regarding the Mechanism of the Cell Destruction by Stimulated Lymphocytes.- The Presence of Cells Expressing Immune-Complex Receptors in Non-Lymphoid Murine Tumors.- T and B Immunodepression during 7,12-dimethylbenz(?) anthracene (DMBA) Carcinogenesis in Mice.- Reversal of a Leukemia Virus-Induced Immunodepression by Macrophages in Vitro and in Vivo.- Tumor Immunology: Interaction between Lymphocytes, Antibodies and Neoplastic Cells: A Summary.- Session 7 Round-Table Discussion: Definition and Functions of IR Genes.- Ir Genes, Phenotypic Expressions and their Interpretation.- T Helpers may be Sensitized by Antigen-Specifically Altered Structures, Which are Coded by the I Region of the H-2 Gene Complex.- Multigenic I Region Control of the Immune Response of Mice to the GLØ and GLT Random Terpolymers.- Overcoming Ir Gene Control of the Response to the Lysozymes.- Genetic Control of the Immune Response to Ordered Peptides of Tyrosine and Glutamic Acid.- Antigen Specific T Cell Factors in the Genetic Control of the Immune Response to poly (Tyr,Glu)-poly (Pro)--poly(Lys).- A Model for Genetic Control of the Immune Response.- Session 8 Regulation of Immune Responses: Suppressor Cells, Their Nature and Function. Enhancing factors.- The Role of Suppression in Immunoregulation.- Immunosuppression by Fetal Liver as a Model for Tolerance to Self.- Suppressor Cells in the Embryonic Thymus Mediate Allograft Tolerance.- Tolerance in Tetraparental Mouse Chimaeras.- Studies on Suppressor T Cells in Tolerance.- Depletion of Suppressor T Cells in Syngeneic Chimeric Mice.- Regulatory Cells in the Bone Marrow.- Suppression by Soluble Factor Released From B Cells.- The Regulatory Influence of the Thymus-Dependent Immune System on the Heterogeneity of Immunoglobulins in Irradiated and Reconstituted Mice.- Interference with Antibody-Feedback by Irradiation, Thymus Cells, the Allogeneic Effect, and Serum Factors.- Effect of Chorionic Gonadotropins on Humoral and Cell-Mediated Immunity.- Augmentation of Cell Mediated Lysis (CML) by THF.- Suppressor Cells and Enhancing Antibodies. Immune Agents of the Facilitation Reaction.- Session 9 Immunopathology.- Immunopathology.- Lymphocyte Surface-Attached Immunoglobulins in Some Clinical Conditions.- Control of Autoimmune Processes by a Thymic Humoral Factor (THF).- Clinical, Immunological and Histopathological Evidence for Thymic Deficiency in Down’s Syndrome (Mongolism).- Immunomorphological Lymph Node Processes in Some Cirrhogenie Liver Diseases.- Casein-Induced Murine Amyloidosis: Amyloid and Immunoglobulin Production and Proliferative Capacity of Splenocytes.- T and B Blocking Factors in Hodgkin’s Disease.- Properties of Transplantable Reticulum Cell Sarcomas in SJL/J Mice.- Skin as a Vehicle for Horizontal Transmission of Gross Passage A Leukemia Virus in Adult Mice.- The Relationship between Phagocytosis, Release of Lysosomal Enzymes and 3’, 5’ Cyclic Adenosine Monophosphate in Mouse Macrophages.- The Still Unsolved Germinal Centre Mystery (Invited Lecture).