Cedar pollinosis in Japan is more prevalent than perennial allergic rhinitis from mite allergens. Allergen-specific subcutaneous immunotherapy (SCIT), while clinically effective, involves problems, such as pain during injections, frequent medical visits, and side effects such as anaphylaxis. Sublingual immunotherapy (SLIT) was developed over-seas and clinical trials for Japanese cedar pollinosis were begun in Japan in 2005.
While a 2008 study showed SLIT symptom scores to be better than those of drug therapy, it was not as satisfactory as SCIT. SLIT was, however, safe and reduced the need for medication.
The immunotherapy mechanism is still unclear and biomarkers have yet to be found in both SCIT and SLIT. We previously showed antigen-induced histamine release from peripheral basophils down-regulated by SCIT, and rates related to their symptoms, so, we studied histamine release in SLIT in a double-blind placebo-controlled study. Changes in peak season/pre season histamine release rates were significantly lower in SLIT compared with placebo.
Regulatory T cells modify immunological response in allergy, but natural regulatory T cells in peripheral blood were not changed by SLIT in our study. Regulatory T cell subtypes were identified recently. We focused on the induced type 1 regulatory T cell (Tr1), which was positive for CD4 and CD25 with negative foxp3 and produces high IL-10. Our samples showed the Tr1 percentage in whole CD4 positive T cells up regulated by SLIT. Cell proliferation of T cells stimulated by the Japanese cedar antigen was suppressed in SLIT and recovered by adding anti-IL-10 antibody or anti-IL-10 receptor antibody. We hope IL-10 from Tr1 may prove to be a key to the immunotherapy mechanism.
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