CX3CL1 and synovial sarcoma: Therefore, macrophages are recruited to the exocrine glands to clear apoptotic cells. Second, another important study also demonstrated that the high expression of CX3CL1 could be observed in the SGs of 10-week-old NOD mice, which is at the pre-SS disease or subclinical stage [23]. CX3CL1, the sole member of the C-X3-C chemokine family, exists in two forms: membrane-bound and soluble.