IL21 and immunoglobulin G4-related sclerosing disease: IgG4-RD patients exhibited increased TGF-β and pro-fibrotic gene expression in γδ T cells.<h4>Conclusion</h4>Within the IL-21-rich microenvironment of IgG4-RD, peripheral Vδ2 T cells acquire a Th2-like phenotype via the IL-21-STAT3-Blimp-1-GATA3 pathway.