Friend or foe: the dichotomous impact of T cells on neuro-de/re-generation during aging

// Brandon Coder 1,* , Weikan Wang 1,2,* , Liefeng Wang 1,3 , Zhongdao Wu 4 , Qichuan Zhuge 2 and Dong-Ming Su 1 1 Institute of Molecular Medicine, University of North Texas Health Science Center, Fort Worth, TX, USA 2 Zhejiang Provincial Key Laboratory of Aging and Neurological Disease Research, First Affiliated Hospital, Wenzhou Medical University, Wenzhou City, Zhejiang, P. R. China 3 Department of Biotechnology, Gannan Medical University, Ganzhou, P. R. China 4 Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, P. R. China * These authors have contributed equally to this work Correspondence to: Dong-Ming Su, email: // Qichuan Zhuge, email: // Keywords : T-cell immunity; aging; neurodegeneration; immunotherapy Received : August 17, 2016 Accepted : October 05, 2016 Published : October 11, 2016 Abstract The interaction between T cells and the central nervous system (CNS) in homeostasis and injury has been recognized being both pathogenic (CD4 + T-helper 1 - Th1, Th17 and γδT) and ameliorative (Th2 and regulatory T cells - Tregs). However, in-depth studies aimed to elucidate the precise in the aged microenvironment and the dichotomous role of Tregs have just begun and many aspects remain unclear. This is due, not only to a mutual dependency and reciprocal causation of alterations and diseases between the nervous and T cell immune systems, but also to an inconsistent aging of the two systems, which dynamically changes with CNS injury/recovery and/or aging process. Cellular immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution - sources of chronic inflammation in the elderly (termed inflammaging(definition)), potentially induces an acceleration of brain aging and memory loss. In turn, aging of the brain via neuro-endocrine-immune network drives total body systemic aging, including that of the immune system. Therefore, immunotherapeutics including vaccination and “protective autoimmunity” provide promising means to rejuvenate neuro-inflammatory disorders and repair CNS acute injury and chronic neuro-degeneration. We review the current understanding and recent discoveries linking the aging immune system with CNS injury and neuro-degeneration. Additionally, we discuss potential recovery and rejuvenation strategies, focusing on targeting the aging T cell immune system in an effort to alleviate acute brain injury and chronic neuro-degeneration during aging, via the “thymus-inflammaging-neurodegeneration axis”.