Autoimmune response to advanced glycosylation end-products of human LDL

• Main Authors: Gabriel Virella, Suzanne R. Thorpe, Nathan L. Alderson, Elias M. Stephan, Daniel Atchley, Francesco Wagner, Maria F. Lopes-Virella
• Format: Article
• Language: English
• Published: Elsevier 2003-03-01
• Series: Journal of Lipid Research
• Subjects: modified lipoproteins; diabetes; immunogenicity of advanced glycosylation end-products-LDL; advanced glycosylation end-products-LDL antibodies
• Online Access: http://www.sciencedirect.com/science/article/pii/S002222752031186X

Advanced glycosylation end-products (AGEs) are believed to play a significant role in the development of vascular complications in diabetic patients. One such product, AGE-LDL, has been shown to be immunogenic. In this report, we describe the isolation and characterization of human AGE-LDL antibodies from the sera of seven patients with Type 1 diabetes by affinity chomatography using an immobilized AGE-LDL preparation that contained primarily the AGE Nε(carboxymethyl)lysine (CML, 14.6 mmol/mol lysine), and smaller amounts of Nε(carboxyethyl)lysine (CEL, 2.7 mmol/mol lysine). The isolated antibodies were predominantly IgG of subclasses 1 and 3, and considered proinflammatory because of their ability to promote FcγR-mediated phagocytosis and to activate complement. We determined dissociation constants (Kd) for the purified antibodies. The average Kd values (4.76 ± 2.52 × 10−9 mol/l) indicated that AGE-LDL antibodies are of higher avidity than oxidized LDL antibodies measured previously (Kd = 1.53 ± 07 × 10−8 ml/l), but of lower avidity than rabbit polyclonal LDL antibodies (Kd = 9.34 × 10−11). Analysis of the apolipoprotein B-rich lipoproteins isolated with polyethylene glycol-precipitated antigen-antibody complexes from the same patients showed the presence of both CML and CEL, thus confirming that these two modifications are recognized by human autoantibodies.A comparative study of the reactivity of purified AGE-LDL antibodies with CML-LDL and CML-serum albumin showed no cross-reactivity.