To investigate a potential association of EOMES expression with T-cell exhaustion and tumor burden, we correlated the numbers of EOMES+ CD8+ T cells with the numbers of exhausted T cells as well as CLL cells in a cohort of leukemic Eμ-TCL1 mice displaying a wide range of tumor load from 10 to 95%. This evidence concerns the gene CD8A and B-cell chronic lymphocytic leukemia.