Endocytosis and transcytosis of gliadin peptides.

BACKGROUND Celiac disease (CD) is a frequent inflammatory intestinal disease, with a genetic background, caused by gliadin-containing food. Some gliadin peptides are not digested by intestinal proteases and can have different biological effects. Gliadin peptides can induce innate and adaptive T cell-mediated immune responses. The major mediator of the stress and innate immune response to gliadin peptides (i.e., peptides 31-43 and 31-55) is the cytokine interleukin-15 (IL-15). Other peptides such as the 33 mer containing the P57-68 sequence, after tissue transglutaminase deamidation, are well presented to T cell in the intestine and can induce an adaptive immune response. FINDINGS In this paper, we review the recent studies on the digestion of gliadin and the peptides released by the digestion process. We will also discuss the mechanisms responsible for the internalization and transcytosis of indigested gliadin peptides in the intestinal epithelium. CONCLUSIONS Gliadin is not completely digested by the intestinal proteases producing bioactive peptides that have different biological effects. These peptides are internalized in the cells by an active process of endocytosis and can traverse the intestinal mucosa with different kinetics and immunological effects. In vivo findings will also be discussed.