APP and Alzheimer disease: In the former, the elicitation of the neuronal ISR by unconventional stressors and, consequently, the unconventional activation of the AβPP-independent iAβ production pathway and switch to the rapid iAβ accumulation phase in the individual neurons occur always at the levels of AβPP-derived iAβ below the T1 threshold (otherwise, the conventional AD would be triggered by the T1 crossing and the occurrence of the unconventional stressor at this stage would be inconsequential).