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 β‐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. J. Neurosci. Res. 47:98–108, 1997. © 1997 Wiley‐Liss, Inc.