Senescent T-lymphocytes are known to accumulate with age, increasing infection risk in middle-aged and elderly individuals. Participation in regular physical activity might offset the deleterious effects of ageing on adaptive immunity . PURPOSE: Examine the impact of estimated VO2max on the frequency of senescent blood T-cells in young and middle-aged men. METHODS: Twenty young (Y; age: 24.8 &#; 3.3) and 20 middle-aged (O; age: 53.9 &#; 3.2) healthy males provided a fasted resting blood sample, completed an assessment of percentage body fat and a physical activity status questionnaire designed to estimate VO2max. Y and O subjects were then divided into Hi and Lo VO2max groups (VO2max; Y: 51.2 &#; 4.4 vs 42.6 &#; 2.2 ml•kg-1•min-1; O: 38.7 &#; 3.3 vs 29.5 &#; 1.3 ml•kg-1•min-1) with n=10 in each group. Isolated lymphocytes were assessed for cell surface expression of senescence (KLRG1+, CD28-, CD57+), naïve (CD45RA+) and memory (CD45RO+) T-cell markers on CD3+ T-cells, CD4+ T-cells and CD8+ T-cells using four-colour flow cytometry. Differences in T-cell phenotype among the 4-groups was analysed by one-way ANOVA. RESULTS: O had a greater proportion of KLRG1+, CD57+, CD28-, KLRG1+/CD57+ and CD45RA-/CD45RO+ CD8+ T-cells than Y, regardless of estimated VO2max. No differences in senescent phenotypes were found between the Hi and Lo VO2max groups in Y. CONCLUSION: A higher estimated VO2max is associated with a lowered frequency of senescent and memory CD4+ and CD8+ T-cells in middle-aged but not younger men.



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