Importance of IL-18-induced Super Th1 Cells for the Development of Allergic Inflammation

Th1 cells, which express IL-18R, produce IFN-gamma in response to Ag and IL-2 and increase further production of IFN-gamma upon additional IL-18 stimulation. They simultaneously produce Th2 cytokines (IL-9 and IL-13), GM-CSF and chemokines (RANTES, MIP-1alpha). Human Th1 cells also produce IFN-gamma and IL-13 in response to anti-CD3 and IL-18. Recently, we demonstrated Th1 cells induce intrinsic type atopic asthma and dermatitis by production of Th1- and Th2-cytokines and chemokines. Here, we review the pathological roles of Th1 cells, stimulated with Ag and IL-18 in vivo, in the pathogenesis of allergic disorders by production of Th1 and Th2 cytokines and chemokines. Based on this unique function of Ag- plus IL-18-stimulated Th1 cells, we proposed to designate them as "super Th1 cells".