Targeting FcγRs to treat antibody-dependent autoimmunity

Self-reactive antibodies represent a significant force in autoimmune disease induction. In antibody-dependent autoimmune syndromes such as immune thrombocytopenia (HP), systemic lupus erythematosus (SLE), myasthenia gravis and rheumatoid arthritis (RA), autoantibodies exert their inflammatory effect through Fc gamma Rs, a well established dass of cell surface receptors that interact with the Fc domain of IgG. Down-regulating Fc gamma R functionality presents an attractive strategy to treat antibody-dependent autoimmune diseases. Various approaches, including nonspecific blocking of the IgG binding site as well as specific targeting using antagonistic monoclonal antibodies, have been explored to modulate the interaction between the Fc portion of IgG and Fc gamma Rs. The exquisite specificity and favorable pharmacokinetics of IgG make monoclonal antibodies a preferred choice. Indeed, the first antagonistic monoclonal antibody against the human Fc gamma RIIIA had shown efficacy in refractory ITP patients; however, the practicality of using anti-Fc gamma RIII antibody as a therapeutic was hindered by its associated adverse events, a phenomenon recapitulated in animal models. In this review, we discuss the role of Fc gamma Rs in autoimmune diseases, and focus on a novel monovalent approach to target Fc gamma Rs to resolve antibody-mediated autoimmunity. Crown Copyright (C) 2016 Published by Elsevier B.V. All rights reserved.