IGHG2 and Alzheimer disease: Moreover, AD showed the lowest levels of corticosteroid-binding globulin (SERPINA6), thyroxine-binding globulin (SERPINA7), lipopolysaccharide-binding protein (LBP), complement C5, Ig lambda-6 chain C region (IGLC6), Ig gamma-2 chain C region (IGHG2; Figure 5A).