Activation marker expression and apoptotic susceptibility of T-cell clones derived from CD34 þ , young and SENIEUR donors Nicola S. Della Valle a , Rita N. Ba ´rcia a , Graham Pawelec b , Julie D. McLeod a, * a Centre for Research in Biomedicine, Faculty of Applied Sciences, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, United Kingdom b Tubingen Ageing and Tumour Immunology Group, Section for Transplantation Immunology and Immunohaematology, Zentrum fu ¨r Medizinische Forschung, Waldho ¨rnlestr. 22, D-72072 Tu ¨bingen, Germany Received 25 June 2003; received in revised form 26 November 2003; accepted 30 November 2003 Abstract T-cell clones (TCC) derived from human peripheral blood lymphocytes of a young control, a healthy elderly (SENIEUR) donor, or from CD34 þ hematopoietic progenitor cells were utilised in this study to examine how in vivo and in vitro ageing affects T-cell apoptotic capability. The role of CD25, CD28 and the intracellular proteins, FLICE-inhibitory protein (FLIP), receptor-interacting protein (RIP) and caspase 3 were investigated. We observed an age-related decline in the expression of the IL-2 receptor a chain CD25, and absence of the co-stimulatory receptor CD28 on three of the four TCC studied. In young donor- and CD34 cell-derived TCC, but not in SENIEUR donor- derived TCC, we observed an age-related increase in susceptibility of the cells to mFas-L-induced apoptosis, which correlated with the age- related decrease of CD25 expression. Expression levels of full-length RIP and FLIP did not show any correlation to apoptotic susceptibility. However, expression levels of the cleaved form of RIP were greatly reduced in the SENIEUR donor-derived TCC, which together with a trend towards increased caspase 3 activity, could indicate an age-related alteration in utilisation of different apoptotic signalling pathways. q 2004 Elsevier Inc. All rights reserved. Keywords: T-cell clones; CD25; Apoptosis; Fas/Fas-L; Receptor-interacting protein; FLICE-inhibitory protein 1. Introduction Ageing is associated with immunosenescence, a term that describes the observed decline in immune regulation and function associated with increased susceptibility to infections, autoimmunity and certain cancers (Solana and Pawelec, 1998). One major biomarker of aged T cells is the reduced expression of the co-stimulatory molecule CD28, which is essential for maximal T-cell activation; its absence could be in part responsible for the reduced activation capacity observed in aged T cells (Pawelec et al., 1999). Surface expression of another cell surface molecule, CD25 (IL-2Ra), which facilitates binding of IL-2 and initiates cell proliferation and differentiation (Theze et al., 1996) has been reported to decrease with age (Dennett et al., 2002; Xu et al., 1993). Upregulated expression of CD28 has been linked to protection against apoptosis (McLeod et al., 1998; Vella et al., 1997), and reduced expression correlates with an increased susceptibility to apoptosis (Dennett et al., 2002). Apoptosis can be induced through death receptors (DR) resulting in the activation of a group of intracellular cysteine proteases called caspases (Schmitz et al., 2000). Caspases play a crucial role in the execution phase of apoptosis and are responsible for many of the biochemical and morpho- logical changes associated with this form of cell death. Two of the most prominent caspases involved with peripheral T-lymphocyte apoptosis are caspase 8 and caspase 3 (Scaffidi et al., 1998). With advancing age, peripheral T cells have been reported to show either an increased or reduced suscepti- bility to Fas-induced apoptosis depending on their cell type. CD4 þ T cells tend to have an increased apoptotic susceptibility with increasing age (Dennett et al., 2002; Pawelec et al., 1996), whereas CD8 þ T cells that reach replicative senescence become resistant to apoptosis (Spaulding et al., 1999). Therefore, as both CD4 and CD8 cells are Fas positive, Fas surface expression does not necessarily render cells susceptible to Fas-L-induced death 0531-5565/$ - see front matter q 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.exger.2003.11.015 Experimental Gerontology 39 (2004) 531–538 www.elsevier.com/locate/expgero * Corresponding author. Tel.: þ 44-1173282531; fax: þ 44-1173282904. E-mail address: julie.mcleod@uwe.ac.uk (J.D. McLeod).