Introduction: 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). Methods: 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. Results: 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. Discussion: 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.
- CD4CD25 regulatory T cells