1. Structure and Function of Immunoglobulins.- Structural Bases of Antibody Functions.- Immunoglobulin Isotypes.- Biological Functions of Antibodies.- Conclusion.- 2. Structure and Expression of Fc Receptors (FcR).- Nomenclature.- Members of the Immunoglobulin Superfamily.- Members of the Animal Lectin Superfamily.- Fc Receptors on Microorganisms.- 3. Cell Activation Via Fc Receptors.- General View of Cell Activation Through Immunoreceptors.- A Model of FcR with Specific Function: The Fc Receptor for IgE (Fc?RI).- A Model of Multifunctional FcR: The Low Affinity Fc Receptors for IgG (Fc?RII and Fc?RIII).- Specific Functions of Several Fc Receptors.- A Nontypical Fc Receptor: The Low-Affinity Receptor of IgE: (CD23).- 4. Fc?R as Negative Coreceptors.- The Immunoreceptor Family.- Fc?RIIB Inhibits BCR-Mediated B Cell Activation.- Fc?RIIB Inhibits FcR-Mediated Mast Cell Activation.- Fc?RIIB Inhibits TCR-Mediated T Cell Activation.- Fc?RIIB Inhibits Cell Activation by all ITAM-Based Immunoreceptors.- The ITIM Motif.- Biochemical Mechanisms of Negative Regulation by Fc?RIIB.- Biological Significance of Negative Regulation by Fc?RIIB.- Conclusion.- 5. Internalization through Receptors for Immunoglobulins.- Endocytosis.- Phagocytosis.- Transcytosis.- Conclusion.- 6. Soluble Fc Receptors.- Soluble Fc? Receptors (sFc?R).- Soluble Fc?R.- Other Soluble FcR.- 7. Fc Receptors and Pathology.- Genetic Aspects of FcR Expression: Relationship to Diseases.- Membrane-Bound Fc?R Involvement in Autoimmunity and Inflammation.- Soluble Fc?R and Fc?R in Pathology: A Marker with a Diagnosis and/or Prognosis Value?.- Membrane-Bound and Soluble FcR Tools for Immunotherapy?.