This is the first comprehensive text to synthesize the literature, describing these functions and presenting the variety of human genetic, mouse model, in vitro and providing clinical evidence of the importance and the dramatic variability of antibodies to influence the immune response. Antibodies represent the correlate of protection for numerous vaccines, and are the most rapidly growing class of drugs, representing a tremendous economic and therapeutic sector ranging from cancer and infectious disease to autoimmunity. Researchers have long understood the variable domain of antibodies, which are responsible for antigen recognition, and can provide protection by blocking the function of their target antigen. However, recent developments in our understanding of the protection mediated by antibodies have highlighted the critical nature of the antibody constant, or Fc domain in the biological activity of antibodies. The Fc domain allows antibodies to link the adaptive and innate immune systems, providing specificity to a wide range of innate effector cells, as well as providing a feedback loop to regulate the character of the immune response via interactions with B cells and antigen-presenting cells. Despite it's nomenclature, a number of factors influence the ability of the constant domain to recruit effector mechanisms. There is a vast literature regarding antibody effector function, indicating that it is a high impact and dynamic area. Provides a comprehensive reference of antibody functions mediated by the Fc domain Clarifies the different mechanisms of IgG activity at the level of the different model systems used Demonstrates the importance of the Fc domain, including protective mechanisms, effector cell types, genetic data, and variability in Fc domain function Covers the role of antibodies in cancer, infectious disease, and autoimmunity, and in both the setting of monoclonal antibody therapy as well as naturally raised antibodies Uniquely concentrates on the therapeutic mechanism of antibodies