TLR7 and neoplasm: While TLR7 and 8 are predominantly expressed in immune cells such as pDCs and B cells (TLR7) as well as monocytes and myeloid dendritic cells (TLR8),55 TLR3 was also found at the surface of fibroblasts and tumor cells.135 Of note, the actual ligands for TLR7 and 8 are RNA cleavage products of ribonucleases (RNases).136,137 So far, RNase T2, RNase 2,138,139 PLD exonucleases140 and RNase 6141 have been identified to be involved in RNA cleavage that enables TLR7/8 activation.