Immune complex formation in IgA nephropathy: a case of the ‘right’ antibodies in the ‘wrong’ place at the ‘wrong’ time?

One of the most striking findings in IgAN is an increase in the circulating levels of poorly galactosylated IgA1 O-glycoforms (Figure 1B). This has been observed in patient populations from North America, Europe and Asia, using a variety of techniques [1–3]. Importantly, two studies of IgA1 eluted from isolated glomeruli have shown that mesangial IgA is enriched with poorly galactosylated IgA1 O-glycoforms, strongly implicating the composition of IgA1 hinge region glycans in the mechanism of IgA1 deposition [4,5]. Novak and colleagues have also reported that these poorly galactosylated IgA1 O-glycoforms are predominantly found in circulating high molecular weight IgA-IC in IgAN [6].