BDNF and Alzheimer disease: Specifically, activated microglia locally produced cytokines such as transforming growth factor-β (TGFβ), insulin-like growth factors-1 (IGF-1), and brain-derived neurotrophic factor (BDNF), these cytokines improved the brain microenvironment and positively affected the AHN, however, in the absence of functional CNS-specific T cells, the expression of these cytokines reduced, correspondingly, the AHN was also reduced [25, 28], it was likely that T cells might directly or indirectly affected the function of the NSCs niche to regulate AHN even under the condition of AD pathology.