Despite the limited age range of our data, the immune parameters showed some age-related changes within our sample; in particular, the CD8+ naïve and memory cells, CD3+ and CD4+ cell activation, and relative values for CD56dim cells counts all increased with age. The consensus of other authors notes that over the full adult range, aging is associated with a decline in T cell function (Ginaldi

et al., 1999, Makinodan et al., 1991 and Pawelec et al., 2002), with decreased pools of naive T and B cells (Utsuyama et al., 1992), increases in the number of memory and effector T and B cells (Linton et al., 1987), an accumulation of late differentiated effector T cells, and a diminished B cell production of immunoglobulins,

probably secondary to a reduced see more activity of T helper lymphocytes (Ben Yehuda et al., 1992 and Antonaci et al., 1987). An age-related up-regulation of HLA-DR+ and CD25+ (activation marker) on CD3+ lymphocytes has also been described in older subjects CX-5461 order (Rea et al., 1999). Early reports suggested that NK cell numbers and activity were unchanged with aging (Fiatarone et al., 1989), but more recent investigators have generally described an increase in the proportion of CD56dim (mature) NK cells, a decrease in the number and/or activity of NK cells, with a decreased affinity for target cells (Grubeck-Loebenstein et al., 2009, Nasrullah and Mazzeo, 1992, Miyaji et al., 1997 and Ruvakina et al., 1998), possibly accentuated in unfit subjects (Ross et al., 2004). The increase in the proportion of mature NK cells may contribute to the decline of NK cell function and thus the increased risk of infections and mortality in elderly individuals (Solana and Mariani, 2000). The numbers of both CD56brightCD16+ and CD56dimCD16+ mature subsets seem to be stable or

even increased in older individuals, whereas the CD56brightCD16− precursor subset is decreased (Beziat et al., 2011, Chidrawar et al., 2006 and Le Garff-Tavernier et al., 2010). A decline in the number of CD56bright NK cells in particular may impair immune regulation, as this cell population plays a central role in cytokine secretion during the innate immune response (Simpson, 2011). It remains uncertain how far adverse changes in immune function medroxyprogesterone can be reversed by an increase of physical activity, although the limited relationships we have found between immune parameters and either aerobic power or muscle strength suggest that the variations of fitness seen in a healthy but non-athletic elderly population have at most a limited impact upon immune function. Simpson (2011) suggested that regular exercise might conserve immune function by forcing T cells into the circulation, encouraging the apoptosis of memory T cells, and thus making “space” for a release of further naive T cells.