Identifying toxic fractions of wheat gluten and their effect on the jejunal mucosa in coeliac disease.

THE TOXICITY OF THREE FRACTIONS (A, B, AND C) OBTAINED BY ULTRAFILTRATION OF A PEPTIC: tryptic digest of gluten has been assessed by serial feeding experiments in patients with treated coeliac disease. The first fraction (A), which contains amino acids and oligopeptides, produced no damage to the jejunal mucosa. The other two fractions (B and C) both caused mucosal damage. Fraction B, which contains the products of digestion of smaller molecular weight, consists of polypeptides which are concentrated in the region of 8000 molecular weight. It contains no gliadin (molecular weight 50 000) or gluten. Ultrastructural evidence of damage was visible six hours after challenge with fraction B and by 10 hours histological abnormalities were also present. Ultrastructural abnormalities occurred early in the epithelial cells and preceded changes in the basement membrane and capillaries. The disaccharidases showed a pronounced depression in all three subjects by 24 hours. The rapid onset of damage after challenge, coupled with the evidence of recovery as soon as 72 hours later, is more in keeping with a direct action on the surface epithelial cells rather than an immune mechanism.