Fig. 2.

Immunoglobulin A1 (IgA1) glycosylation pathway. Hinge region of human IgA1 contains serine (Ser) and threonine (Thr) residues, and some of them become O-glycosylated in B-cells’ Golgi apparatus. The predominating configuration of IgA1 glycans contains galactose (Gal) residues. Circulating IgA1 from IgA nephropathy (IgAN) patients is, to a large degree, galactose deficient and contains terminally sialylated N-acetylgalactosamine (GalNAc). GalNAcT2 UDP-GalNAc-transferase 2, C1GalT1 Core 1 synthase, glycoprotein-N-acetylgalactosamine 3-beta-galactosyltransferase, Cosmc C1GALT1-specific chaperone 1, ST6GalNAc II N-acetylgalactosaminide alpha-2,6-sialyltransferase II, NeuAc N-acetylneuraminic acid (sialic acid)