Functional Characteristics of the High Affinity IgG Receptor, FcγRI

IgG FcRs are important mediators of immunity and play a key role during Ab-based immunotherapy. Within the leukocyte IgG receptor family, only Fc gamma RI is capable of IgG binding with high affinity. Fc gamma RI exists as a complex of a ligand binding a-chain and an FcR gamma-chain. The receptors' alpha-chain can, furthermore, elicit several functions independent of the ITAM-bearing FcR gamma-chain. Functional implications of high-affinity IgG binding and mechanisms underlying FcR gamma-chain-independent signaling remain unclear to this day. In this paper, we provide an overview of past literature on Fc gamma RI and address the implications of recently described interactions between cytosolic proteins and the Fc gamma RI alpha-chain, as well as cytokine-enhanced Fc gamma RI immune complex binding. Furthermore, an analysis of potential polymorphisms within the FCGR1A gene is provided. The Journal of Immunology, 2011, 186: 2699-2704.