Aging disturbs the balance between effector and regulatory CD4+ T cells Kornelis S.M. van der Geest a, ⁎, Wayel H. Abdulahad a , Sarah M. Tete a , Pedro G. Lorencetti a , Gerda Horst a , Nicolaas A. Bos a , Bart-Jan Kroesen b , Elisabeth Brouwer a , Annemieke M.H. Boots a a Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands b Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands abstract article info Article history: Received 9 September 2014 Received in revised form 28 October 2014 Accepted 5 November 2014 Available online 7 November 2014 Section Editor: B. Grubeck-Loebenstein Keywords: Aging Regulatory T lymphocytes Th1 cells Th2 cells Th17 cells Vaccination Healthy aging requires an optimal balance between pro-inflammatory and anti-inflammatory immune re- sponses. Although CD4+ T cells play an essential role in many immune responses, few studies have directly assessed the effect of aging on the balance between effector T (T eff ) cells and regulatory T (T reg ) cells. Here, we determined if and how aging affects the ratio between T reg and T eff cells. Percentages of both naive T reg (nT reg ; CD45RA+CD25 int FOXP3 low ) and memory T reg (memT reg ; CD45RA-CD25 high FOXP3 high ) cells were determined by flow cytometry in peripheral blood samples of healthy individuals of various ages (20–84 years). Circulating Th1, Th2 and Th17 effector cells were identified by intracellular staining for IFN-γ, IL-4 and IL-17, respectively, upon in vitro stimulation with PMA and calcium ionophore. Whereas proportions of nT reg cells declined with age, memT reg cells increased. Both Th1 and Th2 cells were largely maintained in the circulation of aged humans, whereas Th17 cells were decreased. Similar to memT reg cells, the 3 T eff subsets resided primarily in the memory CD4+ T cell compartment. Overall, T reg /T eff ratios were increased in the memory CD4+ T cell compartment of aged individuals when compared to that of young individuals. Finally, the relative increase of memT reg cells in el- derly individuals was associated with poor responses to influenza vaccination. Taken together, our findings imply that aging disturbs the balance between T reg cells and T eff cells. © 2014 Elsevier Inc. All rights reserved. 1. Introduction An optimal balance between pro-inflammatory and anti-inflammatory immune responses is considered essential to preserve health in the el- derly (Franceschi et al., 2007). Tilting the balance towards inflammation in aged individuals, sometimes referred to as ‘inflammaging’, may con- tribute to the development of autoimmunity. Conversely, when the bal- ance shifts towards anti-inflammation, immunity against microbes and tumor cells is hampered (Franceschi et al., 2007). The concept of ‘inflammaging’ and ‘anti-inflammaging’ has been mostly studied in relation to the innate immune system (Franceschi et al., 2007). Aging, however, also has a profound impact on the adaptive immune system (Boraschi et al., 2013). The T cell compartment in particular is affected by aging, as thymic output dramatically drops early in life (den Braber et al., 2012). Consequently, T cell-mediated immunity relies on the maintenance of already existing naive and mem- ory T cells. Ample evidence indicates that late stage memory CD8+ T cells, which lack CD28 expression, expand with age and promote inflammation in the elderly (Weng et al., 2009). In contrast, the CD4+ T cell compartment remains more heterogeneous with age and only few CD28 negative memory CD4+ T cells develop in most aged individ- uals (Weng et al., 2009). CD4+ T cells play a central role in the development and persistence of immune responses. Distinct subpopulations of CD4+ T cells produc- ing specific effector cytokines have been reported (Murphy and Stockinger, 2010). T helper (Th) 1 cells produce IFN-γ, which is impor- tant for immunity against intracellular pathogens. IL-4 producing Th2 cells promote immune responses to parasites, whereas IL-17 producing Th17 cells are involved in protection against extracellular bacteria and yeasts. Various studies have shown that these subsets of effector T (T eff ) cells are either retained or decreased in the circulation of aged humans (Alberti et al., 2006; Karanfilov et al., 1999; Lee et al., 2011). Another subpopulation of CD4+ T cells, termed regulatory T (T reg ) cells, can potently inhibit immune responses (Sakaguchi et al., 2010). Pre- vious studies have shown that both naive (CD45RA+CD25 int FOXP3 low ) and memory (CD45RA-CD25 high FOXP3 high )T reg cells can be identified (Miyara et al., 2009). These T reg cell subsets express different chemokine receptors and have distinct migratory properties (Booth et al., 2010). Naive T reg cells express CCR7 and therefore track into lymphoid organs along with naive T cells (Menning et al., 2007). Memory T reg cells express chemokine receptors similar to T eff cells and are therefore able to home towards sites of inflammation (Duhen et al., 2012). Although few studies Experimental Gerontology 60 (2014) 190–196 Abbreviations: T eff cell, effector T cell; T reg cell, regulatory T cell; nT reg cells, naive regula- tory T cell; memT reg cell, memory regulatory T cell. ⁎ Corresponding author at: Department of Rheumatology and Clinical Immunology, University Medical Center Groningen, Hanzeplein 1, 9700 RB, The Netherlands. E-mail address: k.s.m.van.der.geest@umcg.nl (K.S.M. van der Geest). http://dx.doi.org/10.1016/j.exger.2014.11.005 0531-5565/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Experimental Gerontology journal homepage: www.elsevier.com/locate/expgero