DPP4 and asthma: CD26 and T cells have an important role in the pathogenesis of asthma,6,7 and serum sCD26 is significantly elevated in atopic dermatitis,8 in which a Th2-like immune response is elicited, although the surface expression of CD26 correlates with the production of interferon (IFN)-γ in CD4+ patients with a Th1- like immune reaction.