Telomerase activity in CD4⁺ and CD8⁺ T cells. Telomerase activity was measured by the TRAP assay and is expressed as a percentage of the activity detected in the lung carcinoma cell line GLC₄. (A) Telomerase activity in the original TRAP assay. Telomerase activity in 130, 13, and 1.3 GLC₄ cell equivalents is shown at the left. Specific telomerase activity could still be measured in 130 GLC₄cell equivalents. Addition of RNAse is indicated (+). Abolishment of the signal confirmed specific telomerase activity. No cell extracts were added to the PCR controls a (lysis buffer only) and b (PCR mix). Cell extracts equivalent to 10⁵, 10⁴, and 10³ purified CD4⁺ and CD8⁺ T cells from one healthy control and one representative HIV-infected person early (0.1 year after seroconversion) and late (7.5 years after seroconversion) in infection were analyzed. Addition of the M-ITAS resulted in specific bands (arrow) indicating that Taq polymerase was not limiting. (B) Telomerase activity in freshly isolated purified naive (CD4RA) and memory (CD4RO) CD4⁺ T cells from one HIV-infected individual and one healthy control performed as described in (A), but without M-ITAS. (C) Telomerase activity in freshly isolated naive (CD4RA) and memory (CD4RO) CD4⁺ T cells from six healthy controls and seven HIV-infected individuals. Bars with error bars indicate the mean telomerase activity ± the standard deviation of the population. (D) Representative fluorescence curves showing telomerase activity and M-ITAS (at 145 bp). Lanes 1 and 2, healthy control CD4⁺ and CD8⁺ T cells (100,000 cell equivalents); lanes 3 and 4, HIV⁺ CD4⁺ T cells early and late (100,000, respectively, 75,000 cell equivalents); lanes 5 and 6, HIV⁺ CD8⁺ T cells early and late (identical [id]); lane 7, GLC₄ (100 cell equivalents); and lane 8, lysis buffer.