The percentage of IL-4-producing CD4+ T cells (TH2) was significantly higher in patients with IgG4-RD compared to HC and pSS patients (3.4 ± 0.36% versus 1.5 ± 0.14 and 2.2 ± 0.5%; p < 0.0001 and p = 0.03, respectively). This evidence concerns the gene IL4 and immunoglobulin G4-related sclerosing disease.