Unique carbohydrate-carbohydrate interactions are required for high affinity binding between FcgammaRIII and antibodies lacking core fucose
Claudia Ferrara, Sandra Grau, Christiane Jäger, Peter Sondermann, Peter Brünker, Inja Waldhauer, Michael Hennig, Armin Ruf, Arne Christian Rufer, Martine Stihle, Pablo Umaña, Jörg Benz, Claudia Ferrara, Sandra Grau, Christiane Jäger, Peter Sondermann, Peter Brünker, Inja Waldhauer, Michael Hennig, Armin Ruf, Arne Christian Rufer, Martine Stihle, Pablo Umaña, Jörg Benz
Abstract
Antibody-mediated cellular cytotoxicity (ADCC), a key immune effector mechanism, relies on the binding of antigen-antibody complexes to Fcγ receptors expressed on immune cells. Antibodies lacking core fucosylation show a large increase in affinity for FcγRIIIa leading to an improved receptor-mediated effector function. Although afucosylated IgGs exist naturally, a next generation of recombinant therapeutic, glycoenginereed antibodies is currently being developed to exploit this finding. In this study, the crystal structures of a glycosylated Fcγ receptor complexed with either afucosylated or fucosylated Fc were determined allowing a detailed, molecular understanding of the regulatory role of Fc-oligosaccharide core fucosylation in improving ADCC. The structures reveal a unique type of interface consisting of carbohydrate-carbohydrate interactions between glycans of the receptor and the afucosylated Fc. In contrast, in the complex structure with fucosylated Fc, these contacts are weakened or nonexistent, explaining the decreased affinity for the receptor. These findings allow us to understand the higher efficacy of therapeutic antibodies lacking the core fucose and also suggest a unique mechanism by which the immune system can regulate antibody-mediated effector functions.
Conflict of interest statement
Conflict of interest statement: The authors are employed by F. Hoffmann–La Roche AG and Roche Glycart AG.
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Source: PubMed