SOUTH ASIANS WITH ULCERATIVE-COLITIS EXHIBIT ALTERED LECTIN-BINDING COMPARED WITH MATCHED EUROPEAN CASES

Ulcerative colitis is associated with abnormalities of mucin synthesis and secretion, features that may also be associated with malignant ch ange. It has been shown that South Asians in Britain have a high incid ence of ulcerative colitis but a low incidence of colorectal carcinoma compared with their European counterparts. Previous studies have demo nstrated changes in colonic mucin sialylation and sulphation in both S outh Asian and European cases with ulcerative colitis. This was relate d to disease severity, but changes were also found in quiescent diseas e. The aim of the present study was to determine glycoconjugate expres sion in the colon from South Asian cases and to compare results with t hose from a group of affected Europeans. Glycans were identified in fo rmalin-fixed, paraffin-embedded tissue from 17 South Asian patients wi th ulcerative colitis and from 11 European patients with a similar deg ree of colitis, by the application of 10 biotinylated lectins. These w ere directed against a range of sialyl, fucosyl and 2-deoxy, 2-acetami do-galactosyl sequences, using an avidin-peroxidase revealing system a nd semiquantitative assessment. The South Asian group showed a reducti on in the binding of agglutinins from Sambucus nigra in the apical-mem branous region of enterocytes, and a decrease in apical Maackia amuren sis agglutinin binding. These results suggest that South Asians with u lcerative colitis show a different distribution of terminal N-acetyl n euraminyl residues, either in their alpha-2,6 or alpha-2,3 linkage, co mpared with their European counterparts. The changes in sialylation ob served in European cases compared with normal disease-free control sub jects were present in quiescent disease, but were also related to dise ase activity. Their absence in Asians with ulcerative colitis may impl y an inherent, genetically determined variation in this group, which m ay also play a part in their reduced risk of subsequent malignancy.