Edinburgh Napier University

  T-cell senescence occurs during aging as a consequence of chromosome telomere shortening in response to repetitive antigenic stimulation. Senescent T-lymphocytes normally exhibit a “memory” phenotype (i.e. CD62L-/CD45RA-/CD45RO+) and express CD57 and the killer-cell lectin-like receptor G1 (KLRG1) on the cell surface. Physical exercise elicits a mobilisation of senescent T-lymphocytes into the bloodstream in young subjects (Simpson et al., Immunology, 116, 68. 2005), but it is not known if this also occurs in older adults.
PURPOSE: To determine the frequency of senescent T-lymphocytes in the blood compartment after an acute bout of high-intensity exercise in young (Y) and old (O) subjects.
METHODS: Eight Y (Age: 21 ± 3 yrs) and 8 O (Age: 56 ± 3 yrs) healthy males completed a maximal treadmill walking protocol. Blood lymphocytes isolated before, immediately after and 1h after exercise were assessed for cell surface expression of KLRG1, CD57, CD28, CD45RA, CD45RO, CD62L and lymphocyte subset markers using four-colour flow cytometry.
RESULTS: The numbers of CD3+, CD3+/CD4+, CD3+/CD8+ T-lymphocytes and CD3-/CD56+ NK-cells increased with exercise (p0.05). At rest and immediately after exercise, the percentage of all CD3+/CD8+ T-lymphocytes expressing KLRG1, CD57 and CD45RO was greater in O than Y, whereas Y had a greater expression of CD28, CD45RA and CD62L than O (p0.05).
CONCLUSIONS: Older adults have a greater percentage of senescent CD3+/CD8+ T-lymphocytes in blood than their younger counterparts both at rest and after an acute bout of high-intensity exercise. Exercise elicits a mobilisation of senescent T-lymphocytes into the blood compartment in both Y and O subjects, suggesting that T-cells mobilised by exercise have a reduced capacity for clonal expansion than blood resident T-cells.