Relative telomere length and telomerase activity in blood and tonsils from AIM patients. (A) Telomere lengths were assessed using flow FISH in CD4⁺ and CD8⁺ T cells. Each symbol represents blood and tonsil samples taken from individual patients. (B) Telomere lengths were also investigated in isolated EBV-specific CD8⁺ T cells relative to the CD4⁺ population in the same patient. CD4⁺ (gray histogram) and tetramer-positive CD8⁺ T cells (open histogram) from blood (top panel) and tonsil (bottom panel) were isolated from AIM patients, and telomere lengths were determined by flow FISH. The no-probe control is also shown as a dashed profile. (C) Telomerase activity in blood and tonsils was measured in purified CD8⁺ T cells using the TRAP assay in 3 patients. In patient 3, telomerase activity was also measured in purified tetramer-positive CD8⁺ T cells. Positive and negative controls were run according to manufacturer's instructions. (D) Mean ± SEM telomerase activity for CD8⁺ and tetramer-positive T cells from the 3 separate samples were analyzed.