The International Symposium on the Immunoglobulin A System was organized in observance of the twenty-fifth anni­ versary of the School of Dentistry of the University of Ala­ bama in Birmingham. Immunoglobulin A was chosen as the sub­ ject of the Symposium because of its broad scope in relation to all biologic sciences, as well as for its particular rele­ vance to prevention of the most common human disease--dental caries. More than 500 scientists, from 13 countries, met in Birmingham, Alabama to review critically past and current research on IgA and to outline goals for integrating future investigations of the many facets of the IgA system. It is our pleasure to express sincere appreciation to the following, whose efforts made the Symposium possible: to Dr. Sidney B. Finn, Chairman, and all members of the Twenty­ fifth Anniversary Planning Committee for their advice and assistance; to Dr. Charles A. McCallum, Dean of the School of Dentistry, for his enthusiastic approval and support; to Dr. Frederick W. Kraus, Symposium Chairman, for the countless hours of meticulous planning that ensured the smooth execution of the Symposium; to Ms. Tonnia C. Maddox whose unstinting dedication was indispensable to the organizational success of the meeting; to those who assisted with the transcription of manuscripts and discussions: Ms. Shirley Snow, Ms. Jan Allen, Ms. Janice Buchanan, Ms. Joy Fisher, Ms. Pam Honeycutt, Ms. Mary Huckabee, Ms. Charlotte Hughes, Mr. Stephen Miles, Ms.

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Session A Developmental and Cellular Aspects Chairman: Lars A. Hanson.- The IgA System in Connection with Local and Systemic Immunity.- Origin, Distribution, and Differentiation of IgA-Producing Cells.- Cell Types Contributing to the Biosynthesis of sIgA.- DISCUSSION I.- Gut-Associated Lymphoblasts and Intestinal IgA Plasma Cells.- Bronchial Lymphoid Tissue.- The Origin of Monomeric and Polymeric Forms of IgA in Man.- Cytophilic Properties of IgA to Human Neutrophils.- DISCUSSION II.- Session B Structure, Biosynthesis, and Genetics Chairman: J. Claude Bennett.- Characteristics of SC-Ig Complexes Formed in vitro.- Association of S-IgA Subunits.- Modulation of the Assembly of Immunoglobulin Subunits.- DISCUSSION I - E. C. Franklin, Initial Discussant.- Mechanism of Immunoglobulin Polymer Assembly.- Assembly and Secretion of Immunoglobulin A.- Special Characteristics of the IgA2 Subclass.- Genetics and Evolution of Human Immunoglobulin A.- Physical-Chemical Characteristics of J Chains Obtained from IgM.- DISCUSSION II.- Session C Structure Chairman: Jiri Mestecky.- Isolation, Properties, and Structure of Human IgA Myeloma Globulins.- Amino Acid Sequence Studies of Human IgA Myeloma Proteins.- Structural Studies on a Human IgA1 Myeloma Protein with a Carboxy Terminal Deletion.- The Hinge Peptide of an IgA2m(2) Myeloma Protein.- The Carbohydrate Composition of Glycopeptides Isolated from IgA2 Immunoglobulin.- Mouse IgA Myeloma Proteins with Alpha Chain Deletions: A Comparison with Human Alpha Chains with Deletions.- DISCUSSION I.- Evidence for a Common Synthetic Origin for Secretory and Serum IgA.- Studies on the Primary Structure of Human Secretory Component.- Production of an Fc Fragment from Human Immunoglobulin A by an IgA-Specific Bacterial Protease.- Precipitin Cross-Reactions between Human and Animal J-Chains.- Disulfide Bridges of Human Immunoglobulins A1 and A2.- DISCUSSION II.- Session D Function Chairman: Frederick W. Kraus.- Implications of Secretory Immune System in Viral Infections.- The Role of the Secretory Immune System in Protection Against Agents Which Infect the Respiratory Tract.- The Role of Immunization in Controlling Antigen Uptake from the Small Intestine.- Lack of C3 Activation through Classical or Alternate Pathways by Human Secretory IgA Anti-Blood Group A Antibody.- DISCUSSION I.- Bacterial Adherence to Mucosal Surfaces and Its Inhibition by Secretory Antibodies.- Specificity of Antibodies to Streptococcus Mutans; Significance in Inhibition of Adherence.- Secretory Antibodies in Milk of Swine Against Transmissible Gastroenteritis Virus.- Secretory IgA and Direct Killing of Shigella by Serum Components.- DISCUSSION II.- Session E Clinical Considerations Chairman: Max D. Cooper.- Current Knowledge on Alpha Chain Disease.- The Cellular Basis of IgA Deficiency in Humans.- Alpha Chain Determinants on the Membrane of Immunoglobulin Synthesizing Cells.- Secretory and Serum IgA in Children with Protein-Calorie Malnutrition.- Studies of Secretory Antibodies to E. Coli in Human Urine Compared to the Serum Antibody Content.- Secretory IgA: An Adolescent Coming of Age.- DISCUSSION I.- Types of Size Heterogeneity of IgA Molecules Isolated from Myeloma and Normal Human Serum.- Distribution of IgA Subclasses in Sera and Bone Marrow Plasma Cells of 21 Normal Individuals.- Selective IgA Deficiency and Chronic Obstructive Pulmonary Disease - A Family Study.- DISCUSSION II.- Session F The IgA Antibody Response Implications for Oral Health Chairman: Alexander R. Lawton.- The Induction and Characterization of Secretory IgA Antibodies.- Human Nasal Exocrine IgA Antibody: Formation and Some Activities.- The IgA Antibody-Forming Cell Response in the Rabbit Submandibular Gland Following Several Different Methods of Immunization.- The Establishment of Systemic Immunity Following Antigenic Stimulation of the Lymphoid Tissue of the Gastrointestinal Mucosa.- DISCUSSION I.- The Relationship between Serum and Salivary Antibodies and Cell Mediated Immunity in Oral Disease in Man.- Oral Manifestations of IgA Deficiency.- DISCUSSION II.- Conclusion.- Impressions, Summary, and Questions Raised by the IgA Symposium.- Program Participants.