Bcl-xl-Specific antibody labels activated microglia associated with Alzheimer's disease and other pathological states

This report describes the production of a monoclonal antibody raised against Bcl-xl, and includes an initial study of bcl-xl expression in neuropathology including Alzheimer's disease (AD). Bcl-xl is a potent apoptotic inhibitor and is known to be the predominant Bcl-x isoform in brain. To examine the expression of bcl-xl in aged brain and neurodegenerative disease, we raised a Bcl-xl-specific monoclonal antibody. In aged human brain, the highest bcl-xl expression was observed in cerebellum. By immunohistochemistry, significant bcl-xl expression was detected in reactive microglia of patients with AD and other neurological diseases such as progressive supranuclear palsy. Bcl-xl-positive microglia frequently colocalized with beta-amyloid plaques in AD and with activated astrocytes in non-AD and AD brains, suggesting a general role for Bcl-xl in regions of pathology. High levels of Bcl-xl protein might render microglia more resistant to cytotoxic environments such as areas of neurodegeneration and astrogliosis.