Effect of anti-IgE therapy on food allergen specific T cell responses in eosinophil associated gastrointestinal disorders

Abstract

Background: Anti-IgE therapy inhibits mast cell and basophil activation, blocks IgE binding to both FcεRI and CD23 and down regulates FcεRI expression by antigen (Ag) presenting cells (APCs). In addition to its classical role in immediate hypersensitivity, IgE has been shown in vitro to facilitate Ag presentation of allergens, whereby APC bound IgE preferentially takes up allergens for subsequent processing and presentation. The purpose of this study was to determine whether anti-IgE therapy, by blocking facilitated Ag presentation in vivo, attenuates allergen specific Th2 cell responses.

Methods: To test this hypothesis, food allergen specific T cell responses were examined during a 16-week clinical trial of omalizumab in nine subjects with eosinophilic gastroenteritis and food sensitization. Allergen specific T cell responses were measured using carboxyfluorescein succinimidyl ester dye dilution coupled with intracellular cytokine staining and polychromatic flow cytometry. Four independent indices of allergen specific T cell response (proliferation, Ag dose response, precursor frequency, and the ratio of Th2:Th1 cytokine expression) were determined.

Results: Eight of the 9 subjects had measurable food allergen specific responses, with a median proliferation index of 112-fold. Allergen specific T cell proliferation was limited to CD4 T cells, whereas CD8 T cell did not proliferate. Food allergen specific responses were Th2 skewed relative to tetanus specific responses in the same subjects. In contradistinction to the original hypothesis, anti-IgE treatment did not diminish any of the four measured indices of allergen specific T cell response.

Conclusions: In sum, using multiple indices of T cell function, this study failed to demonstrate that anti-IgE therapy broadly or potently inhibits allergen specific T cell responses. As such, these data do not support a major role for IgE facilitated Ag presentation augmenting allergen specific T cell responses in vivo.

Trial registration: ClinicalTrials.gov identifier NCT00084097.

Figures

Figure 1

CFSE determination of allergen specific CD4 T cell responses. PBMC were activated and stained as per the Material and Methods and then gated on CD3+, violet LIVE/DEAD negative cells (A), and subsequently gated on CD4+, CD8- or CD4-, CD8+ cells (B). After culture with media (C), or peanut antigen extract (D, E), cells were gated on viable (C, D) CD4, or (E) CD8 T cells and CFSE vs. CD4 dotplots were generated.

Figure 2

Effect of anti-IgE therapy on allergen specific T cell proliferation. (A) Allergen specific CD4 T cell proliferation was measured by calculating the percentage of CFSElow cells and the results compared both at baseline and at completion of a 16-week trial of omalizumab. (B) Example of an allergen dose response to peanut Ag for subject 2, performed at baseline (circles) and at study completion (squares). (C) The EC50 for allergen proliferation was compared at baseline and at study completion. (D) The precursor frequency of allergen specific T cells was determined by CFSE dye dilution and compared at baseline and at study completion. Each color/symbol combination represents one subject and one allergen; results in A and D include two allergens examined for each subject.

Figure 3

Allergen specific cytokine staining. PBMC were activated with peanut Ag (A-D, G) or tetanus toxoid (E, F, H), stained for intracellular cytokines, and after gating on CD4+, CFSElow cells, cytokine dots plots of the noted cytokine pairs were generated.

Figure 4

Effect of anti-IgE therapy on allergen specific T cell cytokines. The ratio of IL-4:IFN-γ (A, C) and IL-5:IFN-γ (B, D) producing cells were measured in cultures stimulated with either allergen (A, B) or tetanus toxoid (C, D), and compared at baseline and at study completion. Each color/symbol combination represents one subject and one allergen; results in A and B include two allergens examined for each subject.