Diversity in structure and functions of antibody sialylation in the Fc

Terminal sialic acid residues of glycoconjugates exhibit remarkable functional and structural diversity. They affect biological activity, serum half-life and structural stability of glycoproteins. Alternatively, they act as mediators for pathogens to invade host systems. These surface exposed N-glycans are easily accessible for interactions with receptors, enzymes, etc. In contrast, Fc N-glycans of IgGs are sequestered within the two CH2 domains and exhibit high degree of heterogeneity. They are required for antibody effector functions including binding to C1q protein. Biological significance of Fc glycans has been extensively studied and importance of terminal galactose, bisecting GIcNAc and core fucose has been realized. This review focuses on the recent advances in structure and functions of terminal sialic acid residues of Fc glycans.