IL-7 concentration is increased in nonagenarians but is not associated with markers of T cell immunosenescence

Interleukin-7 is a homeostatic cytokine that contributes to the maintenance of the T cell pool. It also has proinflammatory effects and is involved in the pathogenesis of autoimmune diseases. Due to its homeostatic effects, IL-7 has been proposed as a potential rejuvenation factor for the elderly immune system. We analyzed the correlation of plasma IL-7 concentrations and the proportions of different T cell populations in nonagenarians (n = 163) participating in the Vitality 90+ study. Young individuals (n = 35, aged 19–30 years) were used as controls. The numbers of CD3+, CD14+, CD4+ and CD8+ cells and the expression of the CD28 costimulatory molecule on CD4+ and CD8+ lymphocyte subsets were analyzed using flow cytometry. The plasma IL-7 levels were significantly higher in the nonagenarians compared to the controls (7.86 vs. 5.74 pg/ml, p = 0.004). In the nonagenarians, plasma IL-7 levels correlated inversely with the proportion of CD3+ T cells and directly with the proportion of CD14+ monocytes and plasma C-reactive protein. No correlation was observed between plasma IL-7 levels and the proportions of CD4+CD28− or CD8+CD28− subsets. These results suggest that the IL-7 levels in nonagenarians do not have an inhibitory effect on the development of immunosenescence; rather they are associated with increased inflammation. ► The plasma levels of IL-7 are elevated in nonagenarians. ► The IL-7 levels are correlated with plasma CRP levels and with the proportion of CD14+ cells. ► There is no correlation between IL-7 levels and the markers of T cell immunosenescence. ► Our results do not support the role of plasma IL-7 as an immune system rejuvenating factor.