Autoimmune response to advanced glycosylation end-products of human LDL.
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 chromatography using an immobilized AGE-LDL preparation that contained primarily the AGE N epsilon (carboxymethyl)lysine (CML, 14.6 mmol/mol lysine), and smaller amounts of N epsilon (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 Fc gamma R-mediated phagocytosis and to activate complement. We determined dissociation constants (Kd) for the purified antibodies. The average Kd values (4.76 +/- 2.52 x 10(-9) mol/l) indicated that AGE-LDL antibodies are of higher avidity than oxidized LDL antibodies measured previously (Kd = 1.53 +/- 07 x 10(-8) ml/l), but of lower avidity than rabbit polyclonal LDL antibodies (Kd = 9.34 x 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.
Virella
Gabriel
G
Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC 92425, USA. virellag@musc.edu
Thorpe
Suzanne R
SR
Alderson
Nathan L
NL
Stephan
Elias M
EM
Atchley
Daniel
D
Wagner
Francesco
F
Lopes-Virella
Maria F
MF
D001323:Autoantibodies / Q000097:blood / Q000276:immunology* / Q000302:isolation & purification; D015551:Autoimmunity / Q000276:immunology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000276:immunology; D017127:Glycation End Products, Advanced / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D008077:Lipoproteins, LDL / Q000276:immunology* / Q000378:metabolism*; D010084:Oxidation-Reduction
D001323:Autoantibodies; D017127:Glycation End Products, Advanced; D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein