Methods: Ex-vivo pMHC-II tetramer staining enabled the direct comparison of Walnut-(n-17), Cashew-(n=11), Shrimp-(n=9), and Milk-(n=7) and Egg-(n=6)-specific CD4+ T-cell responses in allergic and non-allergic subjects. CD154+CD4+T-cell assay following short-term stimulation with antigenic-epitopes libraries were used for further functional analyses. The cooperation of CCR4+CCR6+ T-cells in allergic inflammation was assessed utilizing co-cultures of T-cell lines with neutrophils and B-cells.
Results: While different states of differentiation of allergen-specific TH2 cells can be observed between individuals, these cells were confined to food allergic subjects. Interestingly, a sub-population of TH17-like food allergen-specific cells that expressed gut-associated lymphoid tissue (CCR6+β7+) and secondary lymphoid organ homing markers (CCR7+) was also observed, suggesting a link with gastrointestinal clinical manifestation . The cytokine signatures of these T-cells confirmed TH2 and TH17-like profiles. Co-cultures of CCR4+CCR6+ T-cell lines generated neutrophil activation and IgE production by B-cells through the secretion of IL-4 indicating that this sub-population could play a role in food allergic symptoms.
Conclusions: Highly heterogeneous T-cell responses were observed in food allergic subjects raising important questions of the pathophysiological role of each food allergen specific CD4+ T-cell subset in food allergy in general.