.....To investigate how alpha-synuclein affects the neuron, exosomes were derived from alpha-synuclein treated mouse microglia cell line BV-2 cells by differential centrifugation and ultracentrifugation. We found that alpha-synuclein can induce an increase of exosomal secretion by microglia. These activated exosomes expressed a high level of MHC class II molecules and membrane TNF-α. In addition, the activated exosomes cause increased apoptosis. Exosomes secreted from activated microglias might be important mediator of alpha-synuclein-induced neurodegeneration in PD.