The IgG Fc contains distinct Fc receptor (FcR) binding sites: The leukocyte receptors FcγRI and FcγRIIa bind to a region in the Fc distinct from that recognized by neonatal FcR and protein A

Abstract

The CH2-CH3 interface of the IgG Fe domain contains the binding sites for a number of Fe receptors including Staphylococcal protein A and the neonatal Fc receptor (FeRn). It has recently been proposed that file CH2-CH3 interface also contains the principal binding site for an isoform of the low affinity IgG Fc receptor II (FγRIIb). The FcγRI and FcγRII binding sites have previously been mapped to the lower hinge and the adjacent surface of the CH2 domain although contributions of the CH2-CH3 interface to binding have been suggested. This study addresses the question whether the CH2-CH3 interface plays a role in the interaction of IgG with FcγRI and FcγRIIa. We demonstrate that recombinant so..