1. Figure 3 Effect of sialylated glycoforms on IgG activity
Figure 3 | Effect of sialylated glycoforms on IgG activity. a | Depending on the presence (IgG–SA) or absence (IgG–G0) of terminal sialic acid residues, IgG molecules can bind with either type I or type II Fc receptors (FcRs). Type I FcRs trigger innate immune-effector cell activation and pro-inflammatory cytokine release via activating and inhibitory FcγRs, whereas type II FcRs can initiate resolution of inflammation via the release of T helper 2 (TH2) cytokines. b | Regulation of IgG sialylation. Upon IL‑23 secretion by myeloid cells, TH17 cells produce IL‑21 and IL‑22, which induces downregulation of the sialyltransferase β‑galactoside α-2,6‑sialyltransferase 1 (St6Gal1) in B cells. Lack of St6Gal1 expression results in the generation of IgG glycovariants deficient in terminal sialic acid residues. c | Schematic representation of changes in IgG glycosylation during the remitting phase of an autoimmune disease, such as rheumatoid arthritis. Galactosylated and sialylated IgG glycovariants are present before, or following resolution of disease, whereas an increase in the prevalence of IgG–G0 glycovariants might appear shortly before disease initiation, thus generating a time window for use of a preventive or early intervention using anti-inflammatory medications, such as intravenous immunoglobulin (IVIG) infusion, cytokine neutralization, or glucocorticosteriods. α-GPI, glycerolphosphatidylinositol; DCIR, C‑type lectin domain family 4 member A; DC‑SIGN, CD209 antigen; ITAM, immunoreceptor-tyrosine-based activatory motif; ITIM, immunoreceptor-tyrosine-based inhibitory motif; SIGNR1, CD209 antigen-like protein B.
Seeling, M. et al. (2017) Differential antibody glycosylation in autoimmunity: sweet biomarker or modulator of disease activity?
Nat. Rev. Rheumatol. doi: /nrrheum