T-cell function is dampened in parallel to deregulated metabolism in the presence of malignant B cells, especially from CLL origin. PBMCs from HDs were thawed and cultured in the presence or absence of PGA-1, CII, and Mec-1 derived from CLL; LME-1, U-266, and RPMI-8226 derived from MM; and Nalm-6 cells derived from acute B-lymphoblastic leukemia. After 24 hours, anti-CD3/CD28 antibodies were added, and T cells were analyzed 48 hours after stimulation. (A) PBMCs were stained with carboxyfluorescein succinimidyl ester, and CD4⁺ T-cell proliferation was assessed. (B) Brefeldin A and Golgi Stop were added to the coculture 4 hours before analysis to assess cytokine production and degranulation. Percentage of CD4⁺ T cells producing tumor necrosis factor (TNF)-α, interleukin-2 (IL-2), and interferon-gamma (IFNγ) 48 hours after stimulation and percentage of cells expressing CD107A at the cell surface is plotted. After gating on CD4⁺ T cells, activated T cells (CD4⁺CD25⁺) were analyzed for (C) T-cell activation, represented by CD25 levels (gMFI); metabolic capacity, as indicated by (D) glucose uptake (2-NBDG); and (E) mitochondrial mass (MitoTracker green FM). (F) Activated T cells were analyzed for the expression of CD25 and (G) effector function after coculture with CII, Mec-1, U-266, and RPMI-8226. Data are presented as mean ± standard error of the mean (SEM). ∗∗∗P < .001; ∗∗P < .01; ∗P < .05; ns, not significant (1-way analysis of variance [ANOVA] followed by Tukey multiple comparison test or paired t test).