The “resistance to AD” is conferred by the low rate of AβPP-derived iAβ accumulation, as shown in Figure 4, or by the high extent of the T1 threshold, as discussed in the following section, or by the combination of both; in all cases, the T1 threshold is not reached and the second AD stage is not triggered within the lifespan of an individual. Here, APP is linked to Alzheimer disease.