Analysis of food-antigen recognition by immune system using soluble T-cell receptor

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This study aimed to analyze where food antigens are subjected to antigen presentation and recognized by T cells after ingested, using a soluble type of T cell receptor (TCR). The final aim of this study was to elucidate the mechanisms of immune recognition of food antigens. First, using β-lactoglobulin (β-Lg) and ovalbumin, primary food allergens, as model antigens, we analyzed the alteration of T cell functions when TCR-derived signals are altered by varying structure and dose of antigens used to stimulate the T cells. A soluble type of T cell receptor (sTCR) derived from a murine CD4^+ T cell clone specific for β-Lg, G1.19, was prepared using a baculovirus expression system. The sequence recognized by a biotinylation enzyme (BirA) was added downstream of the constant region of sTCR β chain. We confirmed that purified sTCR were biotinylated by BirA in the presence of biotin, and that multimer sTCR were formed by adding streptavidin. G1.19 cells recognize a peptide corresponding to 119-133 region of β-Lg(p119-133)in complex with I-A^b molecule. Proliferative response of G1.19 cells to the antigen was inhibited by adding sTCR to the culture, indicating that sTCR competitively inhibited the binding of TCR on G1.19 cells to the ligand. When the cells were stained with sTCR and fluorescence labeled anti-TCR Cβ antibodies in the presence of anti-MHC class II molecule, specific signals were detected by flow cytometry, indicating sTCR can specifically bind to the complex of the antigenic peptide and a MHC class II molecule.