Molecular and Cellular Mechanisms of Antibody Activity

This book focuses on the function of antibodies in vivo. Recent years have seen an exponential growth in knowledge about the molecular and cellular mechanisms of antibody activity. These new results dramatically changed our view of how antibodies function in vivo. The importance of this class of molecules is demonstrated by the heightened susceptibility to infections of humans and mice with an altered capacity to generate pathogen specific antibody responses. Thus, the majority of our currently available vaccines, such as vaccines against influenza, measles and hepatitis focus on the generation of long lasting antibody responses. Recent evidence from a variety of in vivo model systems and from human patient cohorts has highlighted the exclusive role of cellular Fc-receptors for certain immunoglobulin isotypes and subclasses. With the recent discovery of a human Fc-receptor for IgM all different human immunoglobulin isotypes now have a cellular receptor, providing a feedback mechanism and link between antibodies and the cellular components of the immune system. Moreover it has become clear the complement and Fc-receptor system are tightly connected and regulate each other to ensure a well balanced immune response. Among the immunoglobulin isotypes IgG plays a very important protective role against microbial infections and also as a therapeutic agent to kill tumor cells or autoantibody producing B cells in autoimmune disease. Transfer of our knowledge about the crucial function of Fc-receptors has led to the production of a second generation of therapeutic antibodies with enhanced binding to this class of receptors. Binding of antibodies to Fc-receptors leads to the recruitment of the potent pro-inflammatory effector functions of cells from the innate immune system. Hence, Fc-receptors link the innate and adaptive immune system, emphasizing the importance of both arms of the immune system and their crosstalk during anti-microbial immune responses. Besides this