Although serum under-O-glycosylated IgA1 in IgA nephropathy (IgAN) patients may deposit more preferentially in glomeruli than heavily-O-glycosylated IgA1, the relationship between the glomerular IgA deposition level and the O-glycan profiles of serum IgA1 remains obscure. Here, IGHA1 is linked to IgA glomerulonephritis.