Altered Serum IgG Levels to α-Synuclein in Dementia with Lewy Bodies and Alzheimer's Disease

Natural self-reactive antibodies in the peripheral blood may play a considerable role in the control of potentially toxic proteins that may otherwise accumulate in the aging brain. The significance of serum antibodies reactive against alpha-synuclein is not well known. We explored serum IgG levels to monomeric alpha-synuclein in dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) with a novel and validated highly sensitive ELISA assay. Antibody levels revealed stark differences in patients compared to healthy subjects and were dependent on diagnosis, disease duration and age. Anti-alpha-synuclein IgG levels were increased in both patient groups, but in early DLB to a much greater extent than in AD. Increased antibody levels were most evident in younger patients, while with advanced age relatively low levels were observed, similar to healthy individuals, exhibiting stable antibody levels independent of age. Our data show the presence of differentially altered IgG levels against alpha-synuclein in DLB and AD, which may relate to a disturbed alpha-synuclein homeostasis triggered by the disease process. These observations may foster the development of novel, possibly preclinical biomarkers and immunotherapeutic strategies that target alpha-synuclein in neurodegenerative disease.