S100A9 and Alzheimer disease: S100A9 is fibrillogenic in vitro and accumulates as Corpora amylacea inclusions in the prostate where they are associated with inflammation and possible malignancy.38 Co-incubation of αSN and S100A9 leads to faster aggregation but the formation of less toxic oligomers than those formed by S100A9 alone (although the hybrids are just as toxic as pure αSN oligomers).37 S100A9 also co-aggregates with Aβ, triggering a neuroinflammatory amyloid cascade, which leads to Aβ-containing senile plaque formation in AD.39 The latter two instances may involve cross-seeding.