Immunological studies of aging. IX. Impaired proliferation of T lymphocytes detected in elderly humans by flow cytometry
Staiano-Coico, L.; Darzynkiewicz, Z.; Melamed, M.R.; Weksler, M.E.
Journal of Immunology 132(4): 1788-1792
1984
ISSN/ISBN: 0022-1767 PMID: 6199413 Document Number: 223071
Lymphocytes from humans over the age of 65 incorporate .apprx. 50% less tritiated thymidine [3H-TdR] than do lymphocytes from young donors when cultured with phytohemagglutinin [PHA]. Because lymphocytes from elderly humans are more sensitive to cell cycle arrest induced by 3H-TdR, it was impossible to determine to what extent impaired TdR incorporation reflected a defect in proliferation or the increased sensitivity to the radioactive isotope. Flow cytometry was used to measure the proliferative response of T cells from young and old donors in culture with PHA. It was found that 25% fewer lymphocytes from old as compared to young humans enter the G1 or complete the S phase of the cell cycle. The rate of progression through the cell cycle by activated cells from young and old humans is comparable. Thus, flow cytometry suggested that the difference in TdR incorporation by lymphocytes from old and young donors is attributable equally to a proliferative defect and to cell cycle arrest induced by tritiated thymidine. This conclusion was supported by the fact that the relative impairment of TdR incorporation by lymphocytes from old donors was only 1/2 as great when a 20-min instead of a 24-h pulse of 3H-TdR was used.