It should be noted that ONs with neutralbackbones have not been implicated in immune activation.79,80 Conversely, unmethylated CpG-containing ONs activate another PRR,Toll-like receptor 9 (TLR-9), which stimulates the innate immune system.CpG-containing ONs have therefore been tested clinically as vaccineadjuvants and for cancer immunotherapy.80−82. Here, TLR9 is linked to cancer.