Novel roles for the IgG Fc glycan
IgG antibodies trigger leukocyte activation and inflammation by forming immune complexes that crosslink activating Fc? receptors (Fc?Rs). This is essential to combat infection, but detrimental if antibodies target or cross-react with autoantigens. The high specificity and long serum half-life of IgG antibodies confers tremendous therapeutic potential. Indeed, antibodies have been successfully employed to target cancers, autoreactive B cells, and pro-inflammatory cytokines. Conversely, IgG antibodies can also initiate anti-inflammatory responses. In the form of intravenous immunoglobulin (IVIG), IgGs are routinely administered to treat inflammatory autoimmune diseases. Importantly, the N-linked glycans on the IgG Fc are absolutely required for initiating these IgG effector functions. In fact, the Fc glycan composition dictates IgG affinity to individual Fc?Rs, and in a broader sense, binding to different Fc?Rs classes: activating, inhibitory, and anti-inflammatory (dendritic cell-specific ICAM-3 grabbing nonintegrin, DC-SIGN). The Fc glycan requirements to initiate and suppress inflammation will be discussed herein.
inflammation fc? receptor autoimmune disease dc-sign sialylation