Gluten-derived peptides (e.g., amino-acids 31-49 of alpha-gliadin) have been shown to cause changes typical of celiac disease in the gut. Gluten-derived peptides have mostly been used in in vitro studies. The easiest access to the gastrointestinal system may be the mouth. In the present study we were interested to see whether a synthetic peptide corresponding to amino-acids 31-49 of alpha-gliadin could induce inflammatory changes in the oral mucosa after a local challenge in celiac disease patients.
The challenge was made by injecting the peptide solution at a concentration of 10 microg/ml submucosally into the oral mucosa of 10 celiac disease patients after a gluten-free diet (GFD) and 12 healthy control subjects. B and CD45RO+ T cells, mast cells, CD3+, CD4+, CD8+ lymphocytes, and alphabeta and gammadelta T-cell receptor-bearing (TcR alphabeta, TcR gammadelta) lymphocytes were counted and HLA DR expression was determined. The expression of CD25 and Ki-67 antigen was also examined.
The peptide significantly increased the total number of T cells in the lamina propria of the celiac disease patients. The expression of T-cell activation marker CD25 (IL-2 receptor), but not that of cell proliferation marker Ki-67, was also significantly increased in the lamina propria after peptide challenge. Such a reaction was not observed in the controls. The numbers of CD3+ and CD4+ T cells in the lamina propria were also increased in celiac disease patients after the challenge. The count of TcR gammadelta+ cells was very small in the oral mucosa in celiac disease and showed no increase when the oral mucosa was challenged with the peptide. The expression of HLA DR staining was enhanced after the submucosal peptide challenge in celiac disease; however, the difference was not statistically significant.
The results show that in the celiac disease patients after the peptide challenge the oral mucosal lamina propria responds with a nonproliferative increase of lymphocytes. Thus, submucosal challenge with the peptide 31-49 can be used as an aid in the diagnosis of celiac disease. However, further studies with optimized methodology, including various concentrations of the peptide, adjuvants, other peptides, etc., are warranted, especially because the oral mucosa provides the easiest access to an in vivo peptide challenge in celiac disease.