Note: Intro -- Preface -- References -- Contents -- 22 The Appearance and Diversification of Receptors for IgM During Vertebrate Evolution -- Abstract -- 1 The Adaptive Immune System of Vertebrates -- 2 The Appearance of Receptors Interacting with the Constant Domain of Igs -- 3 The Polymeric Ig Receptor-PIGR -- 4 The FcαµR -- 5 The FcµR -- 6 Concluding Remarks -- Acknowledgements -- References -- 23 Authentic IgM Fc Receptor (FcμR) -- Abstract -- 1 Introduction -- 2 Lymphocyte-Restricted Expression of FcµR -- 3 Unique Ligand-Binding Activity -- 3.1 Fcµ-Specificity, Ligand-Binding Avidity, and Glycosylation -- 3.2 Cis Engagement -- 3.3 Modulatory Effect of FcµR by Cis Engagement -- 3.4 Key Residues in the Transmembrane and Cytoplasmic Tail for FcµR Function -- 4 FcµR Deficiency in Mice -- 5 Epilogue -- Acknowledgements -- References -- 40 FCRLA-A Resident Endoplasmic Reticulum Protein that Associates with Multiple Immunoglobulin Isotypes in B Lineage Cells -- Abstract -- 1 Introduction-Fc Receptors and Their Relatives -- 2 The Identification of FCRLA and FCRLB -- 3 The FCRLA Genome Landscape -- 4 Features of the FCRLA Protein -- 5 FCRLA-Phylogeny and Disease Association -- 6 FCRLA-Expression Pattern and Regulation -- 7 FCRLA is a Soluble Resident ER Protein -- 8 FCRLA is Retained in the ER via its N-terminal Disordered Domain -- 9 FCRLA Associates with Multiple Ig Isotypes in the ER -- 10 TRIM21-One Other Intracellular Fc Receptor that Binds Multiple Ig Isotypes -- 11 FCRLA Function-Facts and Speculations -- 11.1 Facts -- 11.2 Speculations -- Acknowledgements -- References -- 24 Specific IgM and Regulation of Antibody Responses -- Abstract -- 1 Introduction -- 1.1 IgG-Mediated Feedback Suppression -- 1.2 IgG-Mediated Feedback Enhancement -- 1.3 IgE-Mediated Feedback Enhancement -- 1.4 IgM-Mediated Feedback Enhancement. , 2 Basic Parameters of IgM-Mediated Enhancement -- 2.1 Antigens -- 2.2 The IgM Molecule and Mode of Administration -- 2.3 Primary Antibody Responses -- 2.4 Priming for Memory Responses -- 2.5 Avidity of the Enhanced Response -- 2.6 Germinal Center Responses -- 2.7 Specificity of the Enhanced Antibody Response -- 2.8 T Cells and IgM-Mediated Enhancement -- 3 Complement in Antibody Responses to Uncomplexed Antigen -- 4 Complement in Antibody Responses to IgM-Antigen Complexes -- 4.1 Complement Activation by IgM -- 4.2 Complement Receptors 1 and 2, CR1/2, in Antibody Responses to IgM-Antigen Complexes -- 4.3 Cμ13 Knock-in Mice with a Point Mutation in the IgM Heavy Chain Abolishing C1q-Binding -- 4.4 FcμR (Toso/Faim3) and IgM-Mediated Enhancement -- 4.5 Other IgM-Binding Receptors and IgM-Mediated Enhancement -- 4.6 Specific IgM from Wildtype but not Cμ13 Mice, Causes Rapid Deposition of C3 on SRBC in Vivo -- 5 Transport of IgM-Antigen Complexes to Splenic B Cell Follicles -- 6 Summary and Concluding Discussion -- References -- 37 Role of Natural IgM Autoantibodies (IgM-NAA) and IgM Anti-Leukocyte Antibodies (IgM-ALA) in Regulating Inflammation -- Abstract -- 1 Introduction -- 2 Natural Autoantibodies and B1 Cells -- 3 Physiological Role of IgM-NAA -- 4 Physiologic Role of IgM-ALA in Regulating Inflammation -- 4.1 B Cell Clones Obtained from Human Umbilical Cord Produce IgM-ALA that Exhibit Leukocyte Receptor Specificity-Binding of IgM to Leukocytes Was not Mediated by FcμR -- 4.2 IgM-ALA from Different Human Sera Differ in Their Repertoire for Receptor Binding. IgM Regulates Human T Effector Cells and DC Without Affecting Tregs or Chemokine Production -- 4.3 The Function of Murine T Effector Cells, DC and NKT Cells but not Tregs Is Regulated by Binding of Polyclonal IgM to Specific Co-Stimulatory Receptors. , 4.4 Innate Immune Inflammatory Response in Renal Ischemia Reperfusion Injury (IRI) Is Inhibited by IgM-ALA -- 4.5 Ex Vivo Induced Regulatory DC Are Protective in Renal Ischemia. Regulatory DC Require Tregs, B Cells, Circulating IgM and IL10 to Mediate in vivo Protection -- 4.6 Inflammation Mediated by Adaptive Immune Mechanisms in Allograft Transplantation Is Inhibited by Polyclonal IgM -- 4.7 Autoimmune-Mediated Insulitis in NOD Mice Is Inhibited by Polyclonal IgM -- 5 Pathogenic Effects of IgM-NAA Under Non-physiological Conditions -- 6 Conclusion -- References.