Our feasible model of the pathogenesis of IgG4-RD is that chronic stimulation by an unknown antigen induces the polarization and activation of Tfh2 cells that are the disease-causing CD4+ T cells, which may result in the development of germinal centers at affected sites and the generation of IgG4-secreting plasmablasts and plasma cells. Here, CD4 is linked to immunoglobulin G4-related sclerosing disease.