Direct responses of ALL cell lines to CpG ODN. (A) Reverse-transcriptase polymerase chain reaction expression of TLR9 by RFP-ALL cell lines. (B) Direct cytotoxicity of CpG ODN to RFP cell lines. RFP-ALL cell lines were incubated in the presence of CpG ODN 6 μg/mL or PBS for 48 hours, then stained with the viability marker 7-AAD and analyzed by FACS. Percentages of ALL cells that are 7-AAD⁺ are shown. (C) Expression of costimulatory molecules. ALL cell lines were treated in vitro with CpG ODN 6 μg/mL or PBS and incubated for 24 hours. Cells were stained for the costimulatory molecules CD40 and CD86 and assessed by FACS.