Reconstitution of IRF4 expression inhibits the survival of IRF4^−/−Vh11 CLL cells. (A) CLL cells were isolated from spleen of IRF4^−/−Vh11mice and plated on top of S17 stromal cells in RPMI 1640 media containing 10% fetal bovine serum. IRF4-expressing vector and control vector were transfected into cultivated CLL cells using a Nucleofector. Forty-eight hours later, the apoptotic cells in successfully transfected CLL cells (GFP⁺) were analyzed with a kit detecting activated Caspase 3 (BD Pharmingen). FSC, forward scatter. The results of 3 independent experiments were shown. (B) Averages and SDs of 3 independent experiments. *P < .02.