APP and early-onset autosomal dominant Alzheimer disease: Jimenez et al.[132] observed at 6 months, when Aβ begins to accumulate in the APP/PS1 Alzheimer’s disease mouse model, that there were YM1+ cells present in the CNS; however, by 18 months YM1 mRNA levels decreased and there was a massive upregulation in inflammatory factors, suggesting a switch from M2 to M1 as pathology worsened [132].