PRDM1 and B-cell chronic lymphocytic leukemia: The TCL1 mouse model which was employed for the in vivo experiments exhibited all crucial features of anergic CLL cells like impairment of calcium mobilisation, downregulation of IgM and Prdm1 expression (Figs 1d, e and 7c) as well as constitutive activation of ERK1/2 (Fig. 7d).