Reactivity of T Cells with Grass Pollen Allergen Extract and Allergoid

Abstract

Background: Successful allergen–specific immunotherapy is achieved with progressively increasing doses of allergen or allergoid. In order to gain further insight into the mechanism of action of allergoids several in vitro investigations were conducted. Methods: Peripheral blood mononuclear cells (PBMC) from grass pollen allergic and nonallergic subjects were stimulated with either grass pollen extract or allergoid and the proliferation and cytokine production (IL–5, IFN–γ) were measured. Similar investigations were performed with Phl p 5–specific T cell lines (TCL) and clones (TCC). Dendritic cells and PBMC were compared in terms of their relative efficacies as antigen–presenting cells. Results: Both allergen and allergoid induced proliferation and Th2 and Th1 cytokine synthesis by PBMC of allergic subjects, whereas PBMC of nonallergic subjects did not produce IL–5. The maximum level of IL–5 was obtained with a lower concentration than was necessary for maximal IFN–γ production. Higher stimulation doses of allergen and allergoid shifted the cytokine profiles towards a Th1 phenotype. TCL and TCC clearly showed reactivity with both allergen and allergoid when using autologous PBMC for antigen presentation, but compared with the native allergen the reactivity of the allergoid was reduced with most of the TCC. Using dendritic cells for antigen presentation a pronounced increase of stimulation of the TCC especially for the allergoids becomes obvious. Conclusion: In common with grass pollen allergen the corresponding allergoids possess a strong allergen–specific T cell–stimulating capacity. However, the degree of T cell stimulation by the allergoid seems to be dependent on the type of the antigen–presenting cell. Both, allergen and allergoid, can modulate T cell responses in a dose–dependent manner.

T Cell Reactivity with Allergoids: Influence of the Type of APC

“…Allergoids were produced from molecular characterized and standardized extracts by treatment with formaldehyde according to the method described by Marsh et al (7). The source of Phl p 5 and rPhl p 5b had been described previously (14,39).…”

“…The generation of Phl p 5-specific T cell clones from grass pollen allergic individuals was performed as previously described (14,40).…”

“…After 48 h in the incubator (37°C, humidified atmosphere, 5% CO 2 ) 100 l of supernatant was removed, and equal supernatants were pooled and frozen at Ϫ20°C until assayed for cytokines. Immediately after removal of half the medium it was supplemented with fresh medium and 1 Ci [ 3 H]thymidine (AmershamPharmacia, Braunschweig, Germany)/well and further incubated for 16 h. Cells were then harvested on Microbeta filter mats with a 96-well cell harvester (Wallac ADL, Freiburg, Germany) and prepared for measurement in a Microbeta scintillation counter (Wallac ADL) as described previously (14).…”

“…In a previous study we showed that the majority of Phl p 5-specific T cell clones were stimulated by the allergoid when using autologous irradiated PBMC for Ag presentation, although in comparison with the native allergen the magnitude of proliferation was often lower (14). When comparing autologous PBMC with cultivated DC for Ag presentation, a considerable increase in the proliferation could be observed with both allergen and allergoid, and the magnitude of proliferation varied with the individual T cell clone (TCC) 2 (14).…”

“…When comparing autologous PBMC with cultivated DC for Ag presentation, a considerable increase in the proliferation could be observed with both allergen and allergoid, and the magnitude of proliferation varied with the individual T cell clone (TCC) 2 (14). The reduced reactivity of allergoids with autologous PBMC for Ag presentation was attributed to the reduced IgE reactivity (14), because a high proportion of these cells (e.g., B cells) use Ig or Fc receptors for Ag recognition and uptake (15)(16)(17)(18).…”