South Asians with ulcerative colitis exhibit altered lectin binding compared with matched European cases

Abstract

Ulcerative colitis is associated with abnormalities of mucin synthesis and secretion, features that may also be associated with malignant change. It has been shown that South Asians in Britain have a high incidence of ulcerative colitis but a low incidence of colorectal carcinoma compared with their European counterparts. Previous studies have demonstrated changes in colonic mucin sialylation and sulphation in both South Asian and European cases with ulcerative colitis. This was related to disease severity, but changes were also found in quiescent disease. The aim of the present study was to determine glycoconjugate expression in the colon from South Asian cases and to compare results with those from a group of affected Europeans. Glycans were identified in formalin-fixed, paraffin-embedded tissue from 17 South Asian patients with ulcerative colitis and from 11 European patients with a similar degree of colitis, by the application of 10 biotinylated lectins. These were directed against a range of sialyl, fucosyl and 2-deoxy, 2-acetamido-galactosyl sequences, using an avidin--peroxidase revealing system and semiquantitative assessment. The South Asian group showed a reduction in the binding of agglutinins from Sambucus nigra in the apical-membranous region of enterocytes, and a decrease in apical Maackia amurensis agglutinin binding. These results suggest that South Asians with ulcerative colitis show a different distribution of terminal N-acetyl neuraminyl residues, either in their α-2,6 or α-2,3 linkage, compared with their European counterparts. The changes in sialylation observed in European cases compared with normal disease-free control subjects were present in quiescent disease, but were also related to disease activity. Their absence in Asians with ulcerative colitis may imply an inherent, genetically determined variation in this group, which may also play a part in their reduced risk of subsequent malignancy