Telomere length analysis of transduced CD4⁺ T lymphocytes. Representative results of polyclonal CD4⁺ T cells transduced with GFP control (A) and hTERT (B) as well as a clone transduced with hTERT (C) measured by automated flow-FISH. The GFP control-transduced polyclonal population exhibited a decline of telomere length (111 bp/PD) and stopped at 54.0 PDs as indicated at a telomere length of approximately 3.4 ± 0 kb. There was also a decline of telomere length for the hTERT-transduced polyclonal population. The telomere loss was less over time compared to the GFP control (59 bp/PD [B], 58 bp/PD [C]). At later passages, hTERT-transduced polyclonal populations and clones exhibited shorter telomeres than were ever measured in the GFP controls (2.9 ± 0.25 kb [B], 2.3 ± 0.3 kb [C] versus 3.4 ± 0 kb [(A]). Error bars indicate mean ± standard deviation of duplicate measurements.