title: Cellular aging and senescence characteristics of human T-lymphocytes.
abstract: CD28-, CD57+ and KLRG1+ are cell surface markers that have been used to describe senescent T-lymphocytes in humans. However, the relationship among these phenotypes during aging, and their relationship with the concept of in vitro cellular aging have not been well established. Using five-colour flow cytometry, we analyzed peripheral blood T-lymphocytes for their expression of CD28, CD57 and KLRG1 in 11 young (Y) and 11 old (O) apparently healthy human subjects. The proportions of CD28- and CD57+ cells were significantly higher among the T-cell populations of O compared to Y subjects; the proportion of KLRG1+ cells was significantly higher only among CD8+ cells. Populations that were more frequent in the elderly participants were characterised as CD28+ CD57+, CD28- CD57+ or CD28- CD57-. The expression of p16 and p21, considered as markers for in vitro senescence, was higher in CD28+ CD57+ cells than in other subpopulations in both age groups. The expression of p21 was age-related, which was not the case for p16. Thus, although both p16 and p21 are involved in T-cell senescence, they appear to behave differently. CMV infection and shifts in subpopulations are unlikely as explanations of the observed differences. Their higher levels of p16 and p21 expression, coupled with their higher prevalence in the elderly participants make CD28+ CD57+ cells the subpopulation of T-cells most closely corresponding to the concept of senescent cells.
authors.affiliation: Gerontology Department, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Belgium.
authors.forename: Oscar Okwudiri
authors.initials: OO
authors.lastname: Onyema
authors.forename: Rose
authors.initials: R
authors.lastname: Njemini
authors.forename: Ivan
authors.initials: I
authors.lastname: Bautmans
authors.forename: Wim
authors.initials: W
authors.lastname: Renmans
authors.forename: Marc
authors.initials: M
authors.lastname: De Waele
authors.forename: Tony
authors.initials: T
authors.lastname: Mets
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000276:immunology*; D015415:Biomarkers / Q000032:analysis; D018106:CD28 Antigens / Q000032:analysis; D018959:CD57 Antigens / Q000032:analysis; D049109:Cell Proliferation; D016922:Cellular Senescence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000032:analysis; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping / Q000379:methods; D037181:Lectins, C-Type / Q000032:analysis; D008297:Male; D010641:Phenotype; D011971:Receptors, Immunologic; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D015534:Trans-Activators / Q000032:analysis; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018106:CD28 Antigens; D018959:CD57 Antigens; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; C113413:KLRG1 protein, human; D037181:Lectins, C-Type; D011971:Receptors, Immunologic; D015534:Trans-Activators