Evaluation of the Suppressive Capacity of Regulatory T Cells in Food Allergy Research

Regulatory T cells (Treg) exert a crucial role in the suppression of exacerbated T helper (Th) cell responses, including those of type 2 Th (Th2) cells, and in the maintenance of tolerance to environmental antigens and food allergens. The functional capacity of Tregs to suppress Th2 responses has been studied through activation and immunosuppression assays using cells from mice and humans. The immunosuppression assay is an essential in vitro tool that allows the evaluation of the Treg capacity to limit the proliferation and expansion of conventional T cells. This approach enables the determination of the suppressive ability of different Treg subsets. In this chapter, we describe a basic and well-established immunosuppression protocol for human and murine Treg that has been widely applied in food allergy research.

Coculture of Human Dendritic and T Cells for the Study of Specific T Cell-Mediated Responses Against Food Allergens

Dendritic cells (DCs) connect innate and adaptive immunity by sampling, capturing, processing, and presenting the allergen to distinct subsets of CD4+ T cells. In food allergy, this process leads to the generation of allergen-specific Th2 responses and the production of type 2 cytokines that ultimately induce the synthesis of IgE by allergen-specific B cells. In this chapter, we have described different protocols for the isolation of circulating DCs as well as the generation of DC-like cells derived from autologous peripheral monocytes and the human monocytic THP-1 cell line. Coculture of isolated/generated DCs with CD4+ T cells obtained from PBMCs of allergic subjects allows the study of antigen-specific T cell immune responses against food allergens. Early responses upon allergen recognition can be determined by the upregulation of activation markers such as CD154 (CD40 ligand) and the detection of type 2 cytokines (IL-4, IL-5, IL-9, and IL-13). Delayed allergen-specific CD4+ T cell responses induce the proliferation of these cells and the accumulation of type 2 cytokines in coculture supernatants that can be quantified by different approaches (ELISA, EllaTM, and multiplex assays). Together, the protocols described in this chapter can be used to investigate the features of food proteins to induce food allergy, the influence of environmental factors to generate Th2-polarization, the function of DCs to generate differential immune responses in allergic versus tolerant individuals, and to assess the immunomodulating properties of potential therapeutic substances.

Egg yolk lipids induce sensitization to egg white proteins in a mouse model without adjuvant and exacerbate Th2 responses to egg white in cells from allergic patients

This study evaluates the influence of egg lipid fractions in the induction of allergic sensitization to egg white (EW) proteins, using a mouse model of orally adjuvant-free induced allergy. Egg triglycerides (TG) and phospholipids (PL), and to a higher extent the whole egg lipid fraction (EL), induced allergy to EW proteins characterized by increased EW-specific IgG1. EL also increased EW-specific IgE. The administration to mice of a mixture of EW and EL increased the intestinal expression of Il33, Il25, and Tslp, the secretion of IL-33 and IL-6, the expansion of group 2 innate lymphoid cells, the regulation of Gata3, Il4 and Il13, dendritic cell (DC) activation and expression of DC molecules that drive Th2 differentiation. TG promoted the absorption of proteins through the intestinal epithelium, enhancing local Th2 responses, while PL favoured the delivery of antigens to the Peyer's Patches. This differential modulation of the site of absorption of egg proteins determined the different behaviour of TG and PL. Egg yolk lipids also induced activation of Th2-inducing innate responses on intestinal human cells in vitro and enhanced adaptive Th2 functions through the activation of DCs in egg-allergic subjects.