PRF1 and celiac disease: YPQ is one of the relatively abundant tripeptides particularly in 33-mer peptide (LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF) of a2-gliadin which has been considered as celiac super antigen and used as a model epitope in many in vitro studies concerning celiac disease and gluten hydrolysis, whereas, QQP and PFP occur frequently in 26-mer peptide (FLQPQQPFPQQPQQPYPQQPQQPFPQ) of γ-gliadin- another predominant celiac epitope [25, 26].