cqvip:Background:Coeliac disease(CD)is due to an inappropriate T cell mediated response to specific gluten peptides.Measured by interferon γ(IFN-γ)ELISPOT,about half of the gliadin specific T cells induced with in vivo wheat gluten exposure in HLA-DQ2+CD are specific for an α/β-gliadin peptide(p57-73 QE65;QLQPFPQPELPYPQ-PQS)that includes two overlapping T cell epitopes(PFPQPELPY and PQPELPYPQ).Aim:To define minimally substituted variants of p57-73 QE65 universally devoid of IFN-γstimulatory capacity but capable of antagonising IFN-γsecretion from polyclonal T cells specific for p57-73 QE65.Methods:Peripheral blood mononuclear cells collected from 75 HLA-DQ2+CD patients after in vivo gluten challenge were used in overnight ELISPOT assays to screen 218 single or double substituted variants of p57-73 QE65 for cytokine stimulatory and antagonist activity.Results:The region p60-71(PFPQPELPYPQP)and especially p64-67(PELP)was sensitive to substitution.Twelve substitutions in p64-67 stimulated no IFN-γELISPOT response.Among 131 partial agonists identified,45 produced statistically significant inhibition of IFN-γELISPOT responses when cocultured in fivefold excess with p57-73 QE65(n = 10).Four substituted variants of p57-73 QE65 were inactive by IFN-γELISPOT but consistently antagonised IFN-γELISPOT responses to p57-73 QE65,and alsoretained interleukin 10 stimulatory capacity similar to p57-73 QE65.Conclusions:Altered peptide ligands of p57-73 QE65,identified using polyclonal T cells from multiple HLA-DQ2+CDdonors,have properties in vitro that suggest that a single substitution to certain α/β-gliadins could abolish their capacity to stimulate IFN-γfrom CD4 T cells and also have anti-inflammatory or protective effects in HLA-DQ2+CD.
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