Reduced glucose uptake in CLL-derived CD8⁺ T cells can be reversed and is not attributable to competition for glucose with CLL cells. CLL-derived CD8⁺ T cells and age-matched HDs were either positively sorted by fluorescence-activated cell sorting (FACS) or by using a negative T-cell selection kit from Stemcell or left in their PBMC fraction, supplemented with IL-2, and stimulated for 2 days using anti-CD3/CD28 antibodies. After stimulation, cells were analyzed for (A) surface GLUT1 expression (CLL, n = 4; HD, n = 4), (B) glucose uptake (2-NBDG; CLL, n = 5-6; HD, n = 6), and (C) activation (CD71; CLL, n = 5-6; HD, n = 6). (D) CLL cells from PBMCs from CLL patients were purified using CD19 macrophage-activated cell sorting and CD8⁺ T cells were cell sorted afterward. CD8⁺ T cells were either cultured alone, or with CLL cells separated by a transwell (0.2 µm pore size), or cultured together with CLL cells without a transwell in a 1:9 ratio, in the presence of IL-2. Two days after stimulation using anti-CD3/CD28 antibodies, CD8⁺ T cells were analyzed for glucose uptake (2-NBDG) by flow cytometry (CLL, n = 6). (E) Supernatants of PBMCs from CLL patients and age-matched HDs stimulated for 2 days with anti-CD3/CD28 antibodies were analyzed for glucose and lactate concentrations (CLL, n = 6; HD, n = 6). Normality was determined by a D’Agostino and Pearson normality test. The P value was calculated by a Mann-Whitney test (A-C), or a Wilcoxon signed rank test (D-E). Data are presented as mean plus or minus SEM. *P < .05. ns, not significant; TW, transwell.