TLR9 and leukemia: Despite expression of the relevant receptors, in 16-h cytotoxicity assays in which primary B-ALL cells were stimulated with CpG ODN (TLR9), R848 (TLR7), or polyI:C (TLR3) in the absence or presence of syngeneic splenocytes, each TLR agonist exerted only minimal direct cytotoxicity, as measured by changes in leukemia cell viability in the absence of immune effector cells (Figure 1B).