Autoimmunity in Alzheimer's disease: Increased levels of circulating IgGs binding Aβ and RAGE peptides
University of Alabama at Birmingham, Birmingham, Alabama, United States Neurobiology of Aging
(Impact Factor: 5.01).
10/2004; 25(8):1023-32. DOI: 10.1016/j.neurobiolaging.2003.11.001
Plasma samples derived from 33 Alzheimer's disease (AD) and 42 control participants were subjected to several steps to purify specific anti-(amyloid)Abeta IgGs. Affinity-purified IgGs binding the peptide Abeta1-42, a neurotoxic sequence derived from the trans-membrane amyloid precursor protein, exhibited nearly four-fold higher titers in AD patients compared with their control non-AD cohort. Affinity-purified IgGs binding a fragment of the receptor for advanced glycation end products (RAGE) likewise were increased nearly three-fold in AD individuals. Abeta and RAGE IgG titers were negatively correlated with cognitive status, i.e. the more cognitively impaired individuals tended to exhibit higher IgG titers. Abeta IgG titers were negatively correlated with age in the control group, but not with the AD group. Levels of circulating AB- and RAGE-like proteins were not different between AD and control participants, nor was there a relationship between individual IgG titers and the respective Abeta- and RAGE-like proteins. Freshly prepared leukocyte preparations were subjected to flow cytometric analysis. AD individuals exhibited significantly increased populations of cells expressing binding sites for monoclonal antibodies directed against Abeta (5.5-fold), betaAPP (3.5-fold), and RAGE (2.6-fold) relative to the control group. These findings confirm the presence of circulating IgGs specifically directed at proteins implicated in immunological processes linked to AD. The close relationship between titers for Abeta and RAGE IgGs suggests the possibility that the antibodies are being produced in response to a common mechanism or protein complex (with the respective epitopes) linked to the disease.
Available from: Rodrigo Lorenzi
- "Recently, autoantibodies directed against sRAGE were found to be increased in Alzheimer's disease and rheumatoid arthritis  . Our group has also observed increased levels of antisRAGE autoantibodies in haemodialysis patients that might be associated with uraemic vascular dysfunction and with increased sRAGE levels . "
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Morbid obesity increases the risk of cardiovascular disease (CVD). The receptor for advanced glycation end-products (RAGE) is implicated in proinflammatory processes that underlie CVD. Its soluble form (sRAGE) has been proposed as a vascular biomarker. Recently, anti-sRAGE autoantibodies were described and found to be increased in diseases where RAGE is overexpressed. This study aimed to investigate serum levels of anti-sRAGE autoantibodies in morbidly obese patients.
After exclusion based on specific criteria, 150 subjects (50 normoglycemics, 50 glucose-intolerants and 50 diabetics) were randomly recruited from a cohort of 750 obese patients (ABOS). Serum sRAGE and anti-sRAGE autoantibodies were measured before bariatric surgery. Sixty-nine patients were followed for up to 1year after gastric bypass, and their levels of sRAGE and anti-sRAGE autoantibodies measured. The control group consisted of healthy blood donors.
Compared with controls, baseline levels of sRAGE and anti-sRAGE autoantibodies were significantly higher in all obese patients independently of glucose regulation (P<0.001). At 1year after gastric bypass, sRAGE and anti-sRAGE were decreased (P<0.001). The decrease in anti-sRAGE autoantibodies was correlated with an increase in high-density lipoprotein (HDL; P=0.02).
Independently of previous diabetic status, morbid obesity increases sRAGE and anti-sRAGE levels. Weight loss after gastric bypass is followed by a decrease in both titres. The decrease in anti-sRAGE correlates with an increase in HDL.
Available from: Anne Poljak
- "Human natural anti-Aβ antibodies are present in both IgG and IgM repertoire . Aβ binding antibodies are present in healthy humans and AD patients [70,71]. IgM anti-Aβ antibodies showed higher specific activity for Aβ than IgG anti- Aβ antibody , and the ability to clear cerebral Aβ without entering the brain of a mouse model of AD . "
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ABSTRACT: With the promise of disease modifying treatments, there is a need for more specific diagnosis and prognosis of Alzheimer's disease (AD) and mild cognitive impairment (MCI). Plasma biomarkers are likely to be utilised to increase diagnostic accuracy and specificity of AD and cognitive decline.
Isobaric tags (iTRAQ) and proteomic methods were used to identify potential plasma biomarkers of MCI and AD. Relative protein expression level changes were quantified in plasma of 411 cognitively normal subjects, 19 AD patients and 261 MCI patients. Plasma was pooled into 4 groups including normal control, AD, amnestic single and multiple domain MCI (aMCI), and nonamnestic single and multiple domain MCI (nMCI). Western-blotting was used to validate iTRAQ data. Integrated function and protein interactions were explored using WEB based bioinformatics tools (DAVID v6.7 and STRING v9.0).
In at least two iTRAQ replicate experiments, 30 proteins were significantly dysregulated in MCI and AD plasma, relative to controls. These proteins included ApoA1, ApoB100, complement C3, C4b-binding protein, afamin, vitamin D-binding protein precursor, isoform 1 of Gelsolin actin regulator, Ig mmu chain C region (IGHM), histidine-rich glycoprotein and fibrinogen beta and gamma chains. Western-blotting confirmed that afamin was decreased and IGHM was increased in MCI and AD groups. Bioinformatics results indicated that these dysregulated proteins represented a diversity of biological processes, including acute inflammatory response, cholesterol transport and blood coagulation.
These findings demonstrate that expression level changes in multiple proteins are observed in MCI and AD plasma. Some of these, such as afamin and IGHM, may be candidate biomarkers for AD and the predementia condition of MCI.
Available from: Eugeen Vanmechelen
- "The serum anti-Aβ antibody titer was higher in patients with mild cognitive impairment who progressed to AD than in stable cases . The level of auto-antibodies to Aβ did not correlate with the 'likeli-hood of developing AD , although titers were negatively correlated with the cognitive status . Henkel and colleagues  showed that the concentration of the large Aβ-binding particles (LAPs) was highly variable among individuals and that the levels were not disease-specific. "
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ABSTRACT: Therapeutic products that depend on the use of an in vitro diagnostic biomarker test to confirm their effectiveness are increasingly being developed. Use of biomarkers is particularly meaningful in the context of selecting the patient population where the therapeutic treatment is believed to be efficacious (patient enrichment). Currently available 'research-use-only' assays for Alzheimer's disease diagnosis all suffer from non-analyte and analyte-specific interferences. The impact of these interferences on the outcome of the assays is not well understood. The confounding factors are hampering correct value determination in biological samples and are intrinsic to the assay concept, the assay design, the presence in the sample of heterophilic antibodies and auto-antibodies, or might be the result of the therapeutic approach. This review focuses on the importance of assay interferences and considers how these might be minimized with the final aim of making the assays more acceptable as in vitro diagnostic biomarker tests for theranostic use.
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