CpG ODN-induced cytotoxicity against syngeneic ALL. RFP-ALL cell lines were stained with PKH and cocultured in triplicate with either syngeneic murine splenocytes (A) or bone marrow (B) in the presence of CpG ODN or PBS. After 24 hours, cells were harvested, stained for B220 and 7-AAD, and analyzed by FACS. Each graph shows a single representative experiment. Percentages of 7-AAD⁺ ALL cells (PKH⁺/B220⁺) are depicted when cultured with PBS- or CpG ODN-stimulated effector cells at increasing E:T ratios (2-way ANOVA, P < .001 for each graph).