CP and lupus nephritis: In this vein, multiple proteins involved in iron metabolism and handling have been identified as plasma or urinary biomarkers of lupus nephritis and disease flares, including the iron carrier protein transferrin, neutrophil gelatinase-associated lipocalin (NGAL), the ferroxidase enzyme ceruloplasmin, the regulatory protein hepcidin, and the iron storage protein ferritin (3–7).