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.