As shown in Fig. 3a, the frequency of SLAMF7+ population was significantly higher in PD-1+ than PD-1− Th1 cells in IgG4-RD patients (30.8 ± 18.0% vs 12.7 ± 10.3%, p < 0.001), but this trend was not observed between PD-1+ and PD-1− Th1 cells in HCs (9.66 ± 10.0% vs 10.1 ± 7.35%, p = 0.67). This evidence concerns the gene PDCD1 and immunoglobulin G4-related sclerosing disease.