Alzheimer's disease is characterized by the presence of amyloid plaques in the brain, which comprise mainly beta-amyloid peptide and alpha 1-antichymotrypsin. Here, Peter Vandenabeele and Walter Fiers advance the hypothesis that this amyloidogenesis results from an IL-1-/IL-6-mediated acute phase reaction in the brain. They propose possible intracerebral sources of cytokines and acute phase proteins in microglia, astrocytes, neurons and cells of the choroid plexus.