TLR2 and synovial sarcoma: To elucidate the signaling pathway by which the TLR2-stimulated production of IL-23/IL-17 is mediated, we first examined whether IL-23, a major causative factor for Th17 cell amplification, is implicated in the IL-17 production induced by TLR2 stimulation by using PBMCs from the patients with SS.