Lea blood group substance degradation in the human alimentary tract and urinary Lea in coeliac disease.

The Lewis (Lea) blood group substance in alimentary tract liquids is a large molecule. Ileal and jejunal mucosal preparations can act upon it to produce dialysable serologically active Lea. Alimentary tract bacteria cannot produce a similar effect. Plasma, serum and urinary Lea are principally in the form of a dialysable moiety. It is suggested that this dialysable form is produced by mucosal degradation of large-molecule Lea in the alimentary tract. The small-molecule Lea is absorbed, transported in the plasma and then excreted. Both secretor and non-secretor patients with duodenal ulcer and inflammatory bowel disease have normal urinary Lea titres. Non-secretor coeliac patients who have not regenerated normal jejunal mucosa on treatment have significantly reduced urinary Lea titres when compared with healthy individuals. One non-secretor coeliac patient who had regenerated a normal jejunal mucosa on treatment had a normal urinary Lea titre. Coeliac patients have normal titres of salivary Lea.