IL4 and allergic rhinitis: A study which investigated allergen-induced Th2, Th1 and Treg immune responses in peripheral blood mononuclear cells (PBMC) and their association with symptom improvement in allergic rhinitis patients after 3 years of SIT shows that both IL-4 expression and the IL-4/IFN-gamma ratio are decreased in patients with a good therapeutic outcome after 1 year of SIT, whereas the induced Treg and Th1 responses persists over 3 years of SIT [52].