STAT3 and immunoglobulin G4-related sclerosing disease: The impact of IL-21 stimulation and JAK/STAT3 inhibitors on γδ T cell was also evaluated.<h4>Results</h4>Patients with IgG4-RD exhibited decreased peripheral Vδ2 T cells displaying a Th2-like phenotype characterized by elevated Th2 cytokine production and activated IL-21-STAT3-Blimp-1-GATA3 pathway.