S100A9 and Alzheimer disease: Knockout or knockdown of S100a9 decreases the development of memory impairment and neuropathology in transgenic models of AD mice; in humans S100A9 is up-regulated in the hippocampus of AD patients and expressed in microglia in the proximity to Aβ plaques [76, 45], and has been suggested to act as a seeding factor for Abeta accumulation [77].