In vitro cellular aging in T-lymphocyte cultures: analysis of DNA content and cell size.
Like other normal diploid mammalian cells, human T-lymphocytes display a limited in vitro lifespan. Long-term cultures of normal adult peripheral blood T cells, activated in vitro and passaged in the presence of interleukin-2 undergo 23 +/- 7 cumulative population doublings. Cell cycle analysis revealed that in senescent T cell cultures, restimulation with the original antigen resulted in 16-22% of the cells entering S phase, compared to 60% entering cycle in young cultures. In addition, within 1 week of restimulation, the senescent cultures do not increase in cell number, but 93% of the cells return to the G1/G0 DNA content, a proportion typically seen in quiescent (nonrestimulated) cultures. Coculture of early- and late-passage cells at two different ratios excluded a putative inhibitory factor produced by the old cells and similarly eliminated a possible stimulatory product in early cultures. Flow cytometry measure of forward angle light scatter revealed no difference in cell size between early- and late-passage cells, in contrast to the findings with senescent fibroblasts. Thus, while increasing cell size may contribute to the senescent phenotype of fibroblast cultures, it is not a factor in the senescence of human T-lymphocytes, and it is therefore doubtful that alterations in cell size are fundamental to in vitro cellular aging.
Perillo
N L
NL
Department of Pathology and Laboratory Medicine, UCLA School of Medicine 90024-1732.
Naeim
F
F
Walford
R L
RL
Effros
R B
RB
D002453:Cell Cycle; D002455:Cell Division; D048429:Cell Size; D002478:Cells, Cultured / Q000502:physiology; D016922:Cellular Senescence; D004247:DNA / Q000032:analysis; D005347:Fibroblasts; D006801:Humans; D066298:In Vitro Techniques; D013601:T-Lymphocytes / Q000502:physiology*
D004247:DNA