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Pollen-derived non-allergenic substances enhance Th2-induced IgE production in B cells.
Allergy 70, 1450-1460 (2015)
BACKGROUND: B cells play a central role in IgE-mediated allergies. In damaged airway epithelium they are exposed directly to aeroallergens. We aimed to assess whether direct exposure of B cells to pollen constituents affects allergic sensitization. METHODS: B cells from murine splenocytes and from blood samples of healthy donors were incubated for 8 days under Th2-like conditions with aqueous ragweed pollen extracts (Amb-APE) or its constituents. Secreted total IgM, IgG and IgE was quantified by ELISA. Additionally, birch, grass or pine-pollen extracts were tested. The number of viable cells was evaluated by ATP measurements. B cell proliferation was measured by CFSE staining. IgE class switch was analyzed by quantitation of class switch transcripts. In an OVA/Alum i.p.-sensitization mouse model, Amb-APE was intranasally instilled for 11-consecutive days. RESULTS: Upon Th2-priming of murine B cells, ragweed pollen extract caused a dose-dependent increase in IgE production, while IgG and IgM were not affected. The low molecular weight fraction and phytoprostane E1 (PPE1) increased IgE production, Amb a 1 did not. PPE1 enhanced IgE also in human memory B cells. Under Th1-conditions, Amb-APE did not influence immunoglubulin secretion. The IgE-elevation was not ragweed-specific. It correlated with proliferation of viable B cells, but not with IgE class switch. In vivo, Amb-APE increased total IgE and showed adjuvant activity in allergic airway inflammation. CONCLUSIONS: Aqueous pollen extracts, the protein-free fraction of Amb-APE and the pollen-contained substance PPE1 specifically enhance IgE-production in Th2-primed B cells. Thus, pollen-derived non-allergenic substances might be responsible for B cell-dependent aggravation of IgE-mediated allergies.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Adjuvant ; B Cell ; Ige ; Phytoprostane E1 ; Pollen