Effects of anti-allergy drugs on Th1 cell and Th2 cell development mediated by Langerhans cells

It is well known that Langerhans cells (LCs) work as the primary orchestrators in polarization towards T helper type 1 (Th1) or T helper type 2 (Th2) immune responses. In this study, we examined the effects of various anti-allergy drugs against the Th2 cell development by LCs.

The expression of cell surface molecules on LCs was investigated using reverse transcriptase polymerase chain reaction. The effects of anti-allergy drugs on T-cell immunoglobulin and mucin domain-containing protein (TIM)-4 expression in LCs were examined to predict whether they would inhibit Th2 cell development. Next, mice were primed via the hind footpad with ovalbumin (OVA)-pulsed LCs that had been treated with selected anti-allergy drugs. After 5 days, the cytokine response in the popliteal lymph nodes was investigated by enzyme-linked immunosorbent assay. The therapeutic effects of a selected drug on atopic dermatitis (AD) were assessed using AD-like skin lesions of NC/Nga mice.

The first-generation histamine H1 receptorantagonists, cyproheptadine and promethazine, and the second-generation histamine H1 receptor antagonists, emedastine and loratadine, were selected as candidate inhibitors of Th2 cell development. As expected, OVA peptide-pulsed LCs that had been treated with each drug and injected into the hind footpads of mice inhibited Th2 cell development, as represented by down-regulation of interleukin (IL)-4 production. Furthermore, the LCs that had been treated withemedastine also inhibited Th1 cell development, as represented by down-regulation of interferon (IFN)-g production. This additional inhibition of Th1 cell development was accompanied by suppression of CD40 expression in LCs. Therefore, the therapeutic effect of emedastine on AD was examined. Topical application of emedastine significantly suppressed the increase in the skin severity score in NC/Nga mice with AD-like skin lesions. This suppressive effect was associated with a decrease in the production of IFN-g and IL-4 in auricular lymph node cells.

These results suggest that topical application of emedastine to skin lesions of patients with AD may provide clinical benefits through the inhibition of both Th1 cell and Th2 cell development mediated by LCs.