Degeneration process of Lewy bodies in the brains of patients with dementia with Lewy bodies using α-synuclein-immunohistochemistry

We investigated the degeneration process of Lewy bodies (LB) in the brains of dementia with Lewy bodies, using α-synuclein-immunohistochemistry. Intracellular LB, LB-related neurites and some extracellular LB were positively immunostained with anti-α-synuclein antibodies. Concentric LB-bearing neurons had no microglial involvement, while degenerated neurons with ill-defined LB displayed intense microglial involvement. The late stage of extracellular LB were immunoelectron-microscopically composed of loose aggregates of filamentous components with lost α-synuclein-immunoreactivity and penetrated astroglial processes. These findings suggest that microglias are involved during the stages from degenerated LB-bearing neurons to extracellular LB, while astroglias are involved during the stage of extracellular LB. Some intracellular LB were positive for anti-C3d and -C4d antibodies, suggesting that the classical complement pathway is activated in degenerated LB-bearing neurons, inducing microglial activation and neuronal death.