Mechanism and regulation of IgE production in allergy

IgE plays an important role in allergic inflammation. IgE production is regulated by CD4 T cells, in which two functional subsets, Th1 and Th2 cells, exist on the basis of cytokine profiles. Th1 cells produce IL-2 and IFN-gamma that mediate cell-mediated immunity, and Th2 cells produce IL-4, IL-5, IL-6, and IL-10 that mediate humoral immunity. In addition, Th1 and Th2 cells regulate each other. B cell differentiation into IgE producing cells requires two signals, provided by Th2 cells, those through CD40 and IL-4. Humoral immune response, producing IgE, is terminated through the deletion of activated B cells by Th1 cells expressing FasL. Therefore, a balance between Th1 and Th2 cells is critical in the regulation of allergic inflammation. Finally, two possible strategies for allergic diseases are discussed, one is an induction of antigen-specific T cell tolerance and the other is immune deviation to Th1 cells.