Stress Response of Senescent T Lymphocytes: Reduced Hsp70 is Independent of the Proliferative Block

Senescent human T lymphocyte cultures are unable to undergo proliferation, but show no difference from early passage cells in cytotoxic function or surface antigenic profile. A second feature of senescent T cells is the dramatic reduction in hsp70 production in response to heat shock. This decline is associated with a decrease in binding of nuclear extracts to the consensus heat shock element. Interestingly, the progressive decline in the heat shock response of cultured T cells correlates with the percent proliferative life span completed rather than with the actual proliferative activity at the time of heat shock. This suggests that for senescent T cells the reduced ability to respond to heat shock by producing hsp70, although possibly lying at the level of transcriptional control, may nevertheless be unrelated to the reduced DNA synthesis or the diminished proliferative activity also manifested by these cells.