B2M and chronic kidney disease: Overall, these data suggest a role for the FcRn–β2M complex in both normal renal handling of albumin [along with the megalin/cubilin albumin receptor (73–75)] and IgG, as an initiating event in the podocyte injury observed in many immunologically mediated renal diseases, but also the oxidative stress that appears to underlie the progression of proteinuric forms of CKD.