Further evidence of a primary mucosal defect in coeliac disease.

Subfractions of fraction 9, obtained from a peptic-tryptic-pancreatinic digest of wheat gliadin, were subjected to in vitro mucosal digestion and the filtrates examined for residual peptides. Small-intestinal mucosa from four groups of individuals were studied-eight patients with coeliac disease in remission; eight healthy controls; nine first degree relatives of patients with coeliac disease, and six children with recurrent diarrhoea investigated for possible coeliac disease, but in whom the diagnosis was excluded. The highest amounts of residual peptides (measured by scanning densitometer) were detected after digestion with mucosa from patients with coeliac disease and the lowest amounts with the control groups. The results obtained with the group of relatives fell between those of the coeliac disease and control groups, while the recurrent diarrhoea group overlapped the relatives and controls. The residual peptides were derived chiefly from the B-type subfractions of subfractions 1 and 2, obtained by ion-exchange chromatography of fraction 9. These subfractions are rich in glutamine/glutamic acid and proline and have a molecular weight (apparent) of not greater than 1500 Daltons. The results lend further support to the hypothesis of an enzyme deficiency in coeliac disease. A partial enzyme deficiency may exist in some first-degree relatives and in some children with recurrent diarrhoea but with histology of the small intestine within normal limits. HLA-B8 antigen is not correlated with this deficiency, but, when the two factors are associated, they could be related to the manifestation and severity of coeliac disease.