CX3CR1 and synovial sarcoma: In SS patients, NKT cells are significantly reduced in the periphery and infiltrate into the labial glands, possibly mediated by the CX3CL1-CX3CR1 chemotactic axis, with elevated CX3CL1 levels in the glands activating NKT cells and leading to high secretion of IFN-γ and TNF-α, thus contributing to the pathogenesis of SS (96).