The frequency of BAFF-R expression on B cells was significantly lower in IgG4-RD patients compared with HC (76.63 ± 20.85% and 94.13 ± 3.50%; P <0.01), but was comparable to pSS patients (88.96 ± 8.90%; P = 0.066; Figure 2A, B). Here, TNFRSF13C is linked to immunoglobulin G4-related sclerosing disease.