TNFSF13B and immunoglobulin G4-related sclerosing disease: Although IgG4-RD shares many features with pSS, this study revealed that BAFF-R expression was significantly decreased in peripheral B cells in patients with IgG4-RD as compared with pSS and HC, whereas, the serum levels of BAFF in patients with IgG4-RD were significantly higher than those in HC.