PRF1 and allergic disease: Taken together, we speculate that in IgE-allergic AD with HDM allergy, IgE-bearing IDECs responding to the HDM antigens may play a major role in the formation of the characteristic eczematous reaction, i.e., spongiotic formation with the infiltration of CD4+ and CD8+ T cells; in addition, these T cells may be capable of expressing cytokines, such as interferon-gamma, Fas ligand, perforin, and granzyme B, which induce apoptosis in keratinocytes in the epidermis [26,27,28,29].