BDNF and Mental deterioration: Last on the background, it has been demonstrated that immune system dysfunction and the impairment of neurotrophins signaling, such as brain-derived neurotrophic factor (BDNF) and TGF-β1, could promote cognitive decline [65] and neurogenesis [66], while the activation of immune cells (e.g., group 2 innate lymphoid cells) alleviates aging-associated cognitive decline [67].