Changes in the brain induced by amyloid-beta (Aβ) immunotherapy. Comparison of frames (a) and (b) shows the major effects of Aβ immunotherapy upon the brain. There is a decrease in plaques of Aβ and of dystrophic neurites but an increase in the severity of cerebral amyloid angiopathy (CAA), in microglial activation (for the degradation of Aβ plaques), and in the level of soluble Aβ in the brain parenchyma. Neurofibrillary tangles (NFTs) and neuropil threads are still present. AD, Alzheimer disease.