title: Senescent T-lymphocytes are mobilised into the peripheral blood compartment in young and older humans after exhaustive exercise.
abstract: Senescent T-lymphocytes are antigen-experienced cells that express the killer-cell lectin-like receptor G1 (KLRG1) and/or CD57; fail to clonally expand following further antigenic stimulation and prevail in the resting blood of older adults compared to the young. Physical exercise mobilises T-lymphocytes into the bloodstream and is therefore a model with which to compare age-related phenotypes of blood-resident T-cells with those T-cells entering the blood from peripheral lymphoid compartments. Eight young (Y; Age: 21+/-3 years) and 8 older (O; Age: 56+/-3 years) healthy males completed a maximal treadmill exercise 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 three-colour flow cytometry. Lymphocyte subset numbers (CD3+, CD3+/CD4+, CD3+/CD8 and CD3-/CD56+) increased with exercise (p<0.05) but were not different between Y and O. At rest and immediately after exercise, the percentage of CD3+/CD8+ T-lymphocytes expressing KLRG1 and CD45RO was greater in O than Y, whereas Y had a greater expression of CD45RA and CD62L than O. The percentage of all CD3+/CD8+ and CD3+/CD4+ T-lymphocytes expressing KLRG1 and CD57 increased after exercise, but the magnitude of change was not age-dependent. In conclusion, there is a greater proportion of senescent CD3+/CD8+ T-lymphocytes in the blood of older adults compared to young at rest and immediately after exhaustive exercise, indicating that the greater frequency of KLRG1+/CD8+ T-lymphocytes in older humans is ubiquitous and not localised to the peripheral blood.
authors.affiliation: Biomedicine and Sports Science Research Group, School of Life Sciences, Napier University, 10 Colinton Road, Edinburgh EH10 5DT, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Simpson
authors.forename: Cormac
authors.initials: C
authors.lastname: Cosgrove
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Ingram
authors.forename: Geraint D
authors.initials: GD
authors.lastname: Florida-James
authors.forename: Greg P
authors.initials: GP
authors.lastname: Whyte
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Pircher
authors.forename: Keith
authors.initials: K
authors.lastname: Guy
mesh_terms: D000328:Adult; D000375:Aging / Q000276:immunology* / Q000502:physiology; D018106:CD28 Antigens / Q000378:metabolism; D018959:CD57 Antigens / Q000378:metabolism; D002465:Cell Movement / Q000276:immunology; D016922:Cellular Senescence / Q000276:immunology*; D015444:Exercise; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D037181:Lectins, C-Type / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance / Q000276:immunology*; D011971:Receptors, Immunologic; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D018106:CD28 Antigens; D018959:CD57 Antigens; C113413:KLRG1 protein, human; D037181:Lectins, C-Type; D011971:Receptors, Immunologic; D015534:Trans-Activators