Th1 cells, driven by IL-12, mediate cellular immunity, while Th2 cells, stimulated by IL-4, regulate humoral immunity (118, 119).Th1 cells are elevated individuals within IgG4-RD compared to controls, contributing to chronic inflammation and fibrosis through IFN-γ secretion (67). The gene discussed is IL4; the disease is immunoglobulin G4-related sclerosing disease.