Submitted on January 2, 2007
Accepted on March 15, 2007
High-intensity exercise elicits the mobilisation of senescent T-lymphocytes into the peripheral blood compartment in human subjects
Richard J Simpson1*, Geraint D Florida-James1, Cormac Cosgrove1, Greg P Whyte2, Scott Macrae1, Hanspeter Pircher3, and Keith Guy1
1 Biomedicine/Sport and Exercise Science Research Group, School of Life Sciences, Napier University, Edinburgh, United Kingdom
2 Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom
3 Institute for Medical Microbiology and Hygeine, Department of Immunology, University of Freiburg, Freiburg, Germany
* To whom correspondence should be addressed. E-mail: r.simpson{at}napier.ac.uk.
Clonal expansion of T-lymphocytes in response to antigenic stimulation is a fundamental process of adaptive immunity. As a consequence of clonal expansion, some T-lymphocytes acquire a senescent phenotype, fail to replicate in response to further antigenic stimulation, and express the killer-cell lectin-like receptor G1 (KLRG1) and/or CD57. Physical exercise elicits a mobilisation of large numbers of T-lymphocytes into the bloodstream from peripheral lymphoid compartments, but the frequency of senescent cells in the mobilised population is not known. Eight male runners (Age: 29 ± 9yrs; VO2max: 62 ± 6 ml.kg-1.min-1) performed an intensive treadmill-running protocol at 80% VO2max to volitional exhaustion. 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 (CD3, CD4, CD8, CD56) by flow cytometry. The percentage of all CD3+ T-lymphocytes expressing KLRG1 and CD57 increased with exercise (p<0.01). The change in T-lymphocyte KLRG1 expression was attributed to both CD4+ and CD8bright T-cells, with the relative change being greater for the CD8bright population (p<0.01). Mobilised T-lymphocyte populations expressing KLRG1 and CD57 appeared to extravasate the peripheral blood compartment after 1h of recovery. T-lymphocytes with a senescent phenotype are mobilised and subsequently removed from the bloodstream in response to acute high-intensity exercise. This suggests that T-lymphocytes contained within the peripheral lymphoid compartments that are mobilised by exercise are likely to be at a more advanced stage of biological aging and have a reduced capacity for clonal expansion than blood resident T-cells.
