S100A9 and Alzheimer disease: Interestingly, the critical role of S100A9 in Alzheimer’s disease development was demonstrated in a mouse model, where S100A9 production was induced by both the Aβ peptide and the C-terminal fragment of the Aβ precursor protein, while S100A9 knockdown attenuated memory impairment and reduced amyloid plaque burden [21].