Comprehensive, quantitative mapping of T cell epitopes in gluten in celiac disease

Celiac disease is a genetic condition that results in a debilitating immune reaction in the gut to antigens in grain. The antigenic peptides recognized by the T cells that cause this disease are incompletely defined. Our understanding of the epitopes of pathogenic CD4⁺ T cells is based primarily on responses shown by intestinal T cells in vitro to hydrolysates or polypeptides of gluten, the causative antigen. A protease-resistant 33-amino acid peptide from wheat a-gliadin is the immunodominant antigen, but little is known about the spectrum of T cell epitopes in rye and barley or the hierarchy of immunodominance and consistency of recognition of T cell epitopes in vivo. We induced polyclonal gluten-specific T cells in the peripheral blood of celiac patients by feeding them cereal and performed a comprehensive, unbiased analysis of responses to all celiac toxic prolamins, a class of plant storage protein. The peptides that stimulated T cells were the same among patients who ate the same cereal, but were different after wheat, barley, and rye ingestion. Unexpectedly, a sequence from w-gliadin (wheat) and C-hordein (barley) but not a-gliadin was immunodominant regardless of the grain consumed. Furthermore, T cells specific for just three peptides accounted for most gluten-specific T cells, and their recognition of gluten peptides was highly redundant. Our findings show that pathogenic T cells in celiac disease show limited diversity and therefore suggest that peptide-based therapeutics for this disease and potentially other strongly human leukocyte antigen-restricted immune diseases should be possible.