This book provides a detailed description of all kinds of therapeutic antibodies including IgGs, IgAs, IgEs, and IgMs, bispecific antibodies, chimeric antigen receptor antibodies, and antibody fragments. Details about how each of these antibodies interact with their ligands, the immune system, and their targets are provided. Additionally, this book delves into the details of antibody, Fc, and variable chain structures, and how subtle changes in structure, charge, flexibility, post-translational modification, and the ability to bind to natural antibody ligands can result in a significant impact on antibody activity and functionality. Finally, the book explains the critical quality attributes of modern therapeutic antibodies and how to ensure that antibodies entering development have the best possible chance of success.