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Vaccine. 2000 Feb 25;18(16):1661-5.

Costimulatory mechanisms in the elderly.

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Department of Pathology and Laboratory Medicine, UCLA School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095-1732, USA.


Aging is associated with the progressive increase of T cells that lack expression of the CD28 costimulatory molecule. Because CD28/B7 signal transduction is required for proliferation, T cells lacking CD28 gene expression are incapable of clonal expansion. To determine whether CD28- T cells are a separate lineage or, alternatively, are the progeny of formerly CD28+ T cells, we performed cell culture longitudinal analysis on the same population of T cells over time. Repeated antigen-induced T cell division ultimately leads to irreversible cell cycle arrest, shortened telomeres, loss of telomerase inducibility, and total absence of expression of CD28. This in vitro model has elucidated a novel facet of T cell biology that may explain the increased incidence of infection and cancer in the elderly.

[Indexed for MEDLINE]

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