Although serum APRIL levels are elevated in SS patients, local expression in the salivary glands is comparatively lower than BAFF. This indicates that while APRIL may play a systemic role in B cell modulation, its contribution to the inflammatory processes in the exocrine glands may be less significant. Local B cell populations in SS might rely more heavily on BAFF for their survival and function, possibly indicating a dominant role for BAFF in the pathology of SS. This evidence concerns the gene TNFSF13 and synovial sarcoma.