Viability of activated T lymphocytes after exposure to cytarabine, ATRA and valproic acid alone or in combinations. PBMCs derived from healthy blood donors (n = 7) were cultured in vitro with T cell activating anti-CD3 and anti-CD28, and the viability was analyzed by flow cytometry after 4 days of culture in medium alone or with the indicated drugs. (A) The gating strategy to analyze the viability of CD5+ T lymphocytes is shown for a control sample and the corresponding sample of cells exposed to cytarabine 44 μM. T cells were defined as (i) viable when negative staining with the LIVE/DEAD Far Red Fixable Dead Cell Stain, (ii) apoptotic when being LIVE/DEAD Far Red Fixable Dead Cell Stain negative and Annexin V positive, and (iii) dead when being LIVE/DEAD Far Red Fixable Dead Cell Stain positive. (B) The overall results are summarized as stacked bar graphs for the control samples and samples exposed to the indicated drugs or drug combinations. The results are presented as the mean percentages for viable, dead and apoptotic CD5+ T cells. A repeated measure ANOVA with Dunnett’s Multiple Comparison Test was used to determine statistically significant differences (*p <0.05; **p <0.01; ***p <0.001).