SP1 and synovial sarcoma: These results are partially in line with several recent studies that have suggested the use of novel autoantibodies to proteins that are specific to the exocrine glands (SP-1 (salivary gland protein-1), PSP (parotid secretory protein), and CA-6 (carbonic anhydrase VI)) as novel biomarkers for SS that may appear earlier in the course of the disease [23].