reported that high expression of PD-L1/PD-L2 in fibroblasts from HPV-positive head and neck tumor patients is mediated by TLR9, which reduces the expression of PD-L1/PD-L2 when using the TLR9 specific antagonist, ODNTTAGGG (52). This evidence concerns the gene PDCD1LG2 and head and neck neoplasm.