Celiac.com 03/26/2008 - One of the peculiarities of celiac disease is that not all gliadin proteins (peptides) are equal in terms of creating an adverse immune response. Certain peptides are completely broken down during intestinal transport, notably those that are the same size or larger than peptide 57-68. Other peptides, like the peptides 31-49 (P31-41), and the 3-mer gliadin peptide, are transported across the intestinal barrier intact and end up provoking the adverse immune response that is characteristic of celiac disease.

The mechanism by which these peptides move without being broken down has remained unknown. It now looks like scientists have isolated a culprit in the transport of gliadin peptides (in the form of intact gluten particles) across the intestinal barrier.

In people who can tolerate wheat well, gluten is completely broken down, or at least broken down to the point where it won’t provoke an adverse reaction from the person’s immune system. In celiac disease, it seems that certain types of gliadin proteins, notably peptide 31-49 (P31-41), trigger an adverse innate immune response. P31-41 is common to the N-terminus of the A-gliadins and is known to be toxic to people with celiac disease.

The movement of intact gluten particles, particularly peptide 31-49 (P31-41) and the 33-mer gliadin, across the gut barrier is a trigger for the abnormal immune response in celiacs. Until now, the exact mechanism responsible for the movement of undigested gliadin particles across the intestinal barrier remained unknown. The research team showed that a particular receptor, the transferrin receptor CD71 is responsible for the movement of intact gliadin fragments/peptides across the intestinal barrier.

The team of researchers was made up of Tamara Matysiak-Budnik,  Ivan Cruz Moura,  Michelle Arcos-Fajardo,   Corinne Lebreton, Sandrine Ménard, Céline Candalh, Karima Ben-Khalifa ,  Christophe Dugave,  Houda Tamouza, Guillaume van Niel, Yoram Bouhnik, Dominique Lamarque,  Stanislas Chaussade, Georgia Malamut,  Christophe Cellier,  Nadine Cerf-Bensussan, Renato C. Monteiro, and Martine Heyman.

The team undertook the study to help them better understand how undigested gluten is able to migrate across the gut barrier. The size of the study was 53 individuals. The study group looked at 26 patients with active celiac disease, 13 patients who had been following a gluten-free diet for at least 12 months, 4 patients with refractory celiac sprue, and 10 people who were free of celiac disease.

In determining eligibility for the study, the standard for diagnosis of celiac disease was villous atrophy and positive serum tests for anti-gliadin, anti-Tgase, and endomysium IgA antibodies. The standard for refractory celiac sprue was resistance to a gluten-free diet, and persistence of villous atrophy when anti-gliadin IgA anti-bodies were not present. All control subjects were given a routine endoscopy, during which 4-6 consensual biopsy samples were taken, and determined to be free of celiac disease.

Even in people with celiac disease, larger gliadin peptides, like the p57-68 are completely broken down before being transported across the intestinal barrier. Smaller peptides like the like the peptides 31-49 (P31-41), and the 3-mer gliadin peptide, manage to cross the intestinal barrier intact.

Immuno-fluorescence studies revealed that patients with active celiac disease showed greater amounts of IgA at the apical pole of the surface epithelium, while control group and patients with treated celiac disease showed that IgA was isolated in the crypts, and did not appear in the villous epithelium. In people with active celiac disease, CD71 gets over-expressed on the apical pole, while on treated celiacs on a gluten-free diet show normal CD71 expression. For folks with refractory sprue, CD71 gets over-expressed in those individuals with flattened over-proliferation mucosa.

The high rates of binding at the apical surface of enterocytes in patients with active celiac disease indicate that the transferrin receptor CD71 plays a significant role in celiac disease.

JEM VOL. 205, January 21, 2008

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