, Volume 29, Issue 6, pp 752-760
Date: 20 Jun 2009

Specific Immunotherapy to Birch Allergen Does not Enhance Suppression of Th2 Cells by CD4+CD25+ Regulatory T Cells During Pollen Season

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The aim of this study was to investigate the suppressive capacity of CD25+ regulatory T cells on birch allergen-induced T-cell responses during the first birch pollen season after initiation of specific immunotherapy (SIT).


CD25pos and CD25neg T cells were purified from blood of birch-allergic SIT patients and birch-allergic controls, stimulated with birch pollen extract, and analyzed for T-cell proliferation and production of interferon gamma (IFN-γ), interleukin (IL)-5 and IL-10.


We show that allergen-induced proliferation and IFN-γ production were suppressed equally well by CD25pos T cells from SIT patients and controls, while the IL-5 production was not suppressed by either of the groups. IL-10 levels were higher in SIT patients relative to controls only when CD25neg and CD25pos were cultured together. Furthermore, neither FOXP3 levels nor proportions of CD25high T cells were enhanced in SIT patients compared to allergic controls.


These results suggest that the Th2-suppressive capacity of allergen-stimulated CD25pos Treg in vitro is not improved by SIT in spite of increased IL-10 production from T cells.