Impaired induction of mitochondrial biogenesis in CLL-derived CD8⁺ T cells. PBMCs from CLL patients and age-matched HDs were thawed and subsets of CD8⁺ T cells were directly analyzed by flow cytometry. (A) Mitochondrial mass as defined by Mitotracker Green; naive T (Tn) cells: CD27⁺CD45RA⁺CCR7⁺CD95⁻; memory stem cells (Tscm): CD27⁺CD45RA⁺CCR7⁺CD95⁺; memory T cells (Tm): CD27⁺CD45RA⁻; and effector T cells (Te): CD27⁻CD45RA^−/+ (CLL, n = 9; HD, n = 9). (B) PGC-1α and SOD2 expression in CD8⁺ T-cell subsets defined as naive (Tn: CD27⁺CD45RA⁺), memory (Tm: CD27⁺CD45RA⁻), and effector T cells (Te: CD27⁻CD45RA^−/+; CLL, n = 8; HD, n = 8). (C-E) PBMCs were stimulated by using anti-CD3/CD28 antibodies for 2 days and being analyzed for (C) induction of mitochondrial mass, which was calculated by dividing the MFI of Mitotracker Green of stimulated cells by unstimulated cells (CLL, n = 4; HD, n = 4), (D) ΔΨm (CLL, n = 11-12; HD, n = 11-12; unstimulated control is the same as in Figure 4D), and (E) mitochondrial ROS (CLL, n = 11-12; HD, n = 11-12; unstimulated control is the same as in Figure 4E). Normality was determined by a D’Agostino and Pearson normality test. The P value was calculated by a paired Student t test (A), an unpaired Student t test (B, D), a Mann-Whitney test (C), or a Welch test (D-E). Data are presented as mean plus or minus SEM. *P < .05; **P < .005; ***P < .0005; ****P < .0001.