Eosinophilic gastrointestinal disease and peanut allergy are alternatively associated with IL-5+ and IL-5(-) T(H)2 responses

Abstract

Background: Both anaphylactic food allergy and eosinophil-associated gastrointestinal disorders are associated with T(H)2 responses and food-specific IgE, yet they have very different clinical presentations.

Objective: To determine whether the clinical differences between anaphylactic food allergy and eosinophil-associated gastrointestinal disorders are reflected in different T(H)2 responses to foods.

Methods: Subjects with peanut allergy (PA), subjects with allergic eosinophilic gastroenteritis (AEG), and nonatopic subjects were enrolled. Antigen-specific IL-4, IL-5, IFN-gamma, and TNF T-cell responses to peanut, soy, and shrimp were measured by using intracellular cytokine staining and polychromatic flow cytometry.

Results: Two distinct subpopulations of T(H)2 cells were found: IL-5+ T(H)2 (IL-4+, IL-5+) and IL-5(-) T(H)2 (IL-4+, IL-5(-)) cells. Peanut-specific IL-5+ T(H)2 cells were present at a 20-fold greater frequency in AEG versus PA (81 vs 4 per 10(6) CD4 cells; P = .05), whereas there were similar frequencies of IL-5(-) T(H)2 cells (67 vs 41 per 10(6)). For all foods, IL-5+ T(H)2 cells accounted for a significantly greater fraction of the antigen-specific cells in AEG relative to PA (29% vs 4%; P < .0001). In PA but not AEG, IL-5(-) T(H)2 responses to peanut were highly correlated with peanut-specific IgE (r = 0.87 vs 0.55, respectively). All subject groups elicited similar very low-magnitude T(H)1 responses to food antigens.

Conclusion: T(H)2 responses are composed of 2 subpopulations: IL-5+ T(H)2 and IL-5(-) T(H)2 cells. IL-5+ T(H)2 food allergen-specific T cells are singularly associated with AEG, whereas PA is associated with a dominant IL-5(-) T(H)2 response. These results suggest heterogeneity within the T(H)2 cytokine response, with different T(H)2 responses alternatively favoring IgE-mediated or eosinophil-dominant immunopathology.

Trial registration: ClinicalTrials.gov NCT00001756 NCT00084097 NCT00557895.

Fig 1

Detection of food allergen specific T cell responses. A-D: Gating. CD4⁺ T cell expression of CD154 and either IL-4 (E, G) or IL-5 (F, H) after incubation with peanut Ag (E, F) or media (G, H). In a separate experiment, peanut Ag activated cultures were incubated with isotype control (I, J), or anti-MHC class II mAb (K, L), n=5.

Fig 2

AEG is associated with a greater frequency of peanut specific IL-5 producing T cells. The frequency of (A) IL-4, (B) IL-5, (C) IFN-γ and (D) TNF expressing peanut Ag specific CD4 cells was determined for each subject group. Each symbol represents an individual subject. The median value is denoted by a horizontal bar. Intergroup statistics are shown over the brackets.

Fig 3

Food specific T cells exhibit complex cytokine coexpression patterns. Cytokine coexpression by peanut specific T cells from AEG (A, C-E) or PA (B) subjects. (F) Each of the 15 possible cytokine combinations are shown as a proportion of the total peanut response. Individual subjects and medians are denoted by dots and horizontal bars, respectively. All subjects from the 3 groups were studied. *, **, and *** represents p values of ≤0.05, ≤0.01, ≤0.001.

Fig 4

AEG is singularly associated with food allergen specific IL-5⁺ Th2 cells. A-D, the frequency of food Ag specific CD4 cells for each cytokine subpopulation and subject group. E-H, stack graphs depict the median values for each cytokine subpopulation summed to represent the total frequency of Ag specific cytokine producing cells.

Fig 5

Correlation of Th2 responses with IgE and eosinophilia. A, correlation of IL-5⁺ Th2 cells with eosinophil count. Correlation of peanut specific IgE with B, IL-5^- Th2 and C, IL-5⁺ Th2 cells. D, correlation of soy specific IgE with IL-5^- Th2 cells. Linear regression curve fit is shown for AEG (A) and PA subjects (B, C), respectively.