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

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.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.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.ClinicalTrials.gov identifier NCT00084097FcεRI, the high affinity IgE receptor, is expressed by mast cells and basophils, and upon cross-linking by allergen activates these cells, leading to immediate hypersensitivity[1]. FcεRI is also expressed by dendritic cells (DCs) and monocytes and in this capacity FcεRI may have additional functions beyond immediate hypersensitivity. FcεRI expression by APCs can facilitate the IgE mediated uptake of allergen, ultimately resulting in enhanced antigen presentation and increased T cell activation in vitro[2]. In a similar manner, CD23, the low affinity IgE receptor expressed by B cell can a