Analysis of Glycosylation of Immunoglobulin G Using Mass Spectrometry and Its Application

IgG is a key glycoprotein involved in humoral immunity, which plays important roles in removing toxins, activating the corresponding receptors and complement, and regulating the immune response by recognizing specific antigens. The glycosylation of IgG mainly belongs to N-glycosylation, and IgG carries a conserved N-glycosylation site at the site of Asn297 in the constant region, which not only affects the physicochemical properties, such as structure, solubility and stability of IgG, but also impacts its biological function. Therefore, the identification of IgG glycosylation contributes to the deep understanding of immune molecular mechanism, as well as the significance in early diagnosis of disease, prognostic evaluation, and development of therapeutic antibody drugs. In this review, mass spectrometry-based identification methods of IgG glycosylation and their applications were reviewed in the levels of glycan, glycopeptide and intact protein of IgG.