TNFRSF13C and immunoglobulin G4-related sclerosing disease: Meanwhile, the MFI of BAFF-R on mature B cells of IgG4-RD patients (193.1 ± 180.9) was lower than that of pSS patients (374.0 ± 136.5; P = 0.02) and HC (465.5 ± 109.2; P <0.001), whereas there was no significant difference between pSS patients and HC.