Persistence of PRDM1 α transcriptional repression in nonresponsive CLL samples is a result of failure to induce high levels of activating histone modifications. (A) Responsive and nonresponsive CLL samples were treated with: (i) IL-21 + CD40L, or (ii) CpG-ODN and PRDM1α RNA was quantified using quantitative polymerase chain reaction at times up to 4 and 15 hours, respectively. Case numbers are shown in the top left-hand corner of each graph. (B) ChIP experiments showing: (i) H3K9Ac/K14Ac (H3Ac), or (ii) H3K4me3 at the PRDM1 TSS before and after treatment of responsive (R; n = 3) and nonresponsive (NR; n = 3) samples with CpG-ODN. *P = .009.