Usefulness of saliva in predicting clinical effectiveness for sublingual immunotherapy in seasonal allergic rhinitis.

RATIONALE: Development of means to predict clinical effectiveness of sublingual immunotherapy (SLIT) for allergic diseases is a crucial matter.We sought to determine whether whole saliva, which is the first body component contacting with allergen extracts during SLIT, is associated with clinical effectiveness of SLIT in Japanese cedar pollinosis.

METHODS: Blood monocytes or monocytic THP-1 cell were cultured in the presence or absence of either whole saliva or pure saliva with or without treatments including filtration and blockade of TLR2 and/or TLR4 signaling, after which amounts of IL-10 in the supernatants were measured. Whole saliva-induced IL-10 production by THP-1 cell was compared between patients with symptom-free and disease-onset following SLIT.

RESULTS: Both monocytes and THP-1 cell produced substantial amounts of IL-10 in response to whole saliva. The IL-10 production was significantly reduced in response to pure saliva and 0.2 mm-filtered saliva. Simultaneous treatment with polymyxin B and TL2.1, the neutralizing antibody against TLR2, also reduced the production. Amounts of IL-10 produced by THP-1 cell in response to whole saliva collected just before SLIT were significantly higher in symptom-free patients than disease-onset patients following SLIT. Such differences were not seen in saliva collected 3 months after the initiation of SLIT or those collected during the peak pollen dispersal.

CONCLUSIONS: Our results provide a basis why sublingual route is effective and preferable in allergen immunotherapy. Amounts of IL-10 produced by THP-1 in response to saliva collected prior to SLIT initiation may become a predictive marker of SLIT.