Upregulation of telomerase activity in CD4⁺and CD8⁺ T cells after in vitro stimulation. PBMC were cultured in vitro for 4 days with CD3 MoAbs and telomerase activity was analyzed in extracts prepared from purified CD4⁺ and CD8⁺ T cells. (A) Telomerase activity in 500, 100, and 50 cell equivalents from one healthy control (HIV-) and one representative HIV-positive individual (HIV⁺) early and late (3 years after seroconversion, 1 year before AIDS) in infection is shown as described in Fig 1A. (B) Representative fluorescence curves showing telomerase activity in activated CD4⁺ and CD8⁺ T cells and M-ITAS. Lanes 1 and 2, CD4⁺ and CD8⁺ T cells from a second healthy control (10,000 cell equivalents); lanes 3 and 4, CD4⁺and CD8⁺ T cells from HIV⁺ early in infection (id); lanes 5 and 6, CD4⁺ and CD8⁺ T cells from HIV⁺ late in infection (id); lanes 7 and 8, GLC₄ (100 cell equivalents) and lysis buffer. (C) Telomerase activity in CD4⁺ and CD8⁺ T cells after activation in vitro in four HIV-infected individuals early and late in infection as analyzed with the original TRAP assay.