title: Proliferation and apoptosis of human CD8(+)CD28(+) and CD8(+)CD28(-) lymphocytes during aging.
abstract: It is commonly believed that the age-related decrease in the ratio CD28(+)/CD28(-) among CD8(+) T cells reflects replicative senescence of the lymphocytes. To verify this claim we measured the proliferation of CD8(+)CD28(+) and CD8(+)CD28(-) subsets by flow cytometry after PHA treatment of mononuclear lymphocytes from donors of different age, including centenarians. The fraction of CD28(+) cells decreases from ca. 80 to 40% (young to centenarians, respectively) with increasing age of the donors. Stimulation by PHA results in an increase in the ratio of CD28(+) relative to CD28(-) in all age groups. We found that not only CD8(+)CD28(+) but also CD8(+)CD28(-) cells were capable of proliferation. Moreover, the fraction of proliferation-competent CD28(-) cells was higher in the older donors compared with the younger ones. While PHA treatment led to apoptosis (as measured by DNA content and caspase-3 activation) of more than 20% of all lymphocytes, in the CD8(+) subset only ca. 10% died, irrespective of their CD28 status. Altogether, we showed over-representation of proliferating CD8(+)CD28(-) cells in aged people, which might not be particularly prone to undergo apoptosis.
authors.affiliation: Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteur St., 02-093 Warsaw, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Brzezińska
authors.forename: Adriana
authors.initials: A
authors.lastname: Magalska
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Szybińska
authors.forename: Ewa
authors.initials: E
authors.lastname: Sikora
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology*; D018106:CD28 Antigens / Q000097:blood*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology*; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000276:immunology; D006801:Humans; D016130:Immunophenotyping; D008213:Lymphocyte Activation / Q000276:immunology; D008875:Middle Aged; D010835:Phytohemagglutinins / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology*
chemical_list: D018106:CD28 Antigens; D010835:Phytohemagglutinins