Aberrant glycosylation in IgA nephropathy (IgAN). Immunoglobulin A nephropathy (IgAN) patients exhibit circulating IgA1 with reduced galactose (Gal) and/or sialic acid (Neu5Ac) and increased exposure of N-acetylgalactosamine (GalNAc). These IgA glycoforms fix complement and in mesangial cells regulate integrin expression, enhance nitric oxide synthase (NOS) activity, decrease endothelial growth factor synthesis, meanwhile depressing proliferation and increasing apoptotis. Drugs can be targeted to the effects enhanced by aberrantly glycosylated IgA1 on mesangial cells. Recent data suggest that aberrant IgA1 glycosylation may modulate clinical expression and progression of IgAN.