Specific immunotherapy prevents increased levels of allergen-specific IL-4-and IL-13-producing cells during pollen season

Background: Specific allergen immunotherapy (SIT) is effective for treatmen t of IgE-mediated diseases; however, the mechanisms of action still remain unclear. Earlier, we showed that IL-4 and IL-13 are produced in response to specific allergens. The aim of this study was to investigate whether these cytokine responses were affected by allergen SIT, and, furthermore, to eva luate the effect of SIT on allergen-specific IgE and IgG4 levels. Methods: Blood samples from pollen-sensitized individuals were collected be fore the pollen season (before treatment) and during the pollen season (aft er SIT or placebo treatment). Peripheral blood mononuclear cells were activ ated in vitro with allergens and the numbers of IL-4-, IL-13-, IL-10-, and IFN-gamma -producing cells were determined by ELISPOT. Serum levels of alle rgen-specific IgE and IgG4 were measured by RAST and ELISA, respectively. Results: The numbers of IL-4- and IL-13-producing cells were shown to be in creased in the placebo group during the pollen season, an increment which w as absent in patients receiving allergen SIT. We found an increase in aller gen-specific IgG4 in the SIT-treated individuals, but not in the placebo gr oup. Both groups displayed elevated specific IgE levels during the pollen s eason. Conclusions: Taken together, our data show a downregulation of IL-4- and IL -13-producing cells in peripheral blood after SIT, suggesting induction of nonresponsiveness/tolerance or a redistribution of these cells. Furthermore , we demonstrate that SIT acts on antibody production by increasing the spe cific IgG4 levels.