CX3CR1 and synovial sarcoma: In addition, CX3CL1 protein levels were elevated in the serum of SS patients; transcriptional profiling of peripheral B cells showed upregulation of CX3CR1 expression (69); and histological assessments showed upregulation of the mRNA levels of CX3CL1 and CX3CR1 in the salivary glands of SS patients (70).