PSEN1 and Alzheimer disease: Recently, we showed that the widely used APPswe/PS1ΔE9 (APP/PS1) double transgenic mouse model of AD, like patients with AD, show an age-dependent sigmoidal increase in cortical Aβ plaque load and a chronic neuroinflammatory reaction becoming prominent around 12 months of age [12], at a time point when the transgenic mouse shows cognitive and behavioural deficits [13].