CD8A and B-cell chronic lymphocytic leukemia: The phenotypic results were confirmed by the expression of two master regulators of CD8+ T cell differentiation, T-bet and Eomes.19–24 EBV- and CMV-specific CD8+ T cells of CLL patients showed higher expression levels of the transcription factor T-bet, which drives CD8+ T cell effector function (Fig. 2B, global CD8+ T cells in Supplemental Figure 3B).