Increase of immunoglobulin G3 subclass is related to brain autoantibody in Alzheimer's disease but not in Down's syndrome.

Medical University of South Carolina, Department of Microbiology and Immunology, Charleston 29425.

The proportions of IgG subclasses (G1, G2, G3 and G4) were quantified in sera from Alzheimer's disease (AD) patients, older Down's syndrome (DS) patients and age-matched controls. The levels of IgG1, IgG2 and IgG4 were normal in AD patients, but the proportions of IgG3 were significantly elevated in 9 of 20 (45%) patients (0.803 +/- 0.141 mg/ml; p less than 0.001) compared to the level found in age-matched controls (0.471 +/- 0.161 mg/ml; n = 10). The IgG3 level in the remaining 11 AD patients was slightly lower than the controls (0.385 +/- 0.104 vs. 0.471 +/- 0.161 mg/ml), but it did not reach statistical significance (p = 0.149). In contrast, patients with DS displayed imbalance of IgG2, IgG3, and IgG4 subclasses; they had significantly increased IgG3 but decreased IgG2 and IgG4 levels. The IgG1 level was within normal range. Moreover, a majority of AD sera (8 of 9) with elevated IgG3 concentration were positive for brain autoantibody. The remaining 11 AD sera without elevated IgG3 level, all DS sera and all control sera were negative for brain autoantibody. This finding indirectly suggests that brain autoantibody is mainly due to IgG3 subclass, at least in one subset of AD patients.

Detection of brain autoantibodies in the serum of patients with Alzheimer's disease but not Down's syndrome.

The immunofluorescent staining of antibodies specifically binding to rat brain tissue sections was investigated in 95 human sera including 30 cases of Alzheimer's disease. A high incidence of specific antibrain antibody was found among Alzheimer's patients (57% positive) compared to other neurological disease controls (only 8% positive) or normal young and aged healthy controls (none positive).

Intravenous immunoglobulin and Alzheimer's disease immunotherapy.

Department of Molecular Microbiology and Biotechnology, George S Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Tel Aviv, Israel. beka@post.tau.ac.il

Amyloid-beta peptide (Abeta) contributes to the acute progression of Alzheimer's disease (AD) and has become the main target for therapeutics. Active immunization with Abeta in individuals with AD has been efficacious; however, some patients developed side effects, possibly related to an autoimmune response. Evidence that intravenous immunoglobulin (IVIg), an FDA-approved purified immunoglobulin fraction from normal human donor blood, shows promise of passive immunotherapy for AD is reviewed. Investigations into the molecular effects of IVIg on Abeta clearance, using the BV-2 cellular microglia line, demonstrate that IVIg dissolves Abeta fibrils in vitro, increases cellular tolerance to Abeta, enhances microglial migration toward Abeta deposits, and mediates phagocytosis of Abeta. Preliminary clinical results indicate that IVIg, which contains natural antibodies against the Abeta, warrants further study into its potential to deliver a controlled immune attack on the peptide, avoiding the immune toxicities that have had a negative impact on the first clinical trials of vaccine against Abeta.

PMID: 17330405 [PubMed - indexed for MEDLINE]