TNFSF13B and synovial sarcoma: Belimumab, a monoclonal antibody targeting BAFF, significantly reduces ESSDAI, ESSPRI, and average dryness VAS scores in SS patients, with most B-cell biomarkers (including IgG, IgA, IgM, free κ, and λ light chains), RF titers, and average B-cell counts showing improvement (155).