In this study, CLL B-cell differentiation was associated with upregulation of IRF4 and BLIMP1 with no measurable levels of BCL6, features also observed in the in vitro TLR9, PMA, and CD40 differentiation systems of CLL B-cells (14, 18, 20, 21, 196). Here, IRF4 is linked to B-cell chronic lymphocytic leukemia.