Similar to the AD hippocampi, the neocortical areas of AD brains have also shown an abundance of Aβ and S100A9 amyloid plaques, in which the immunostaining pattern for Aβ, S100A9 and fibrillar antibodies were perfectly overlapped (Fig. 2a, b, e and supplemental file 2). Here, S100A9 is linked to Alzheimer disease.