Lipopolysaccharide (LPS) of manyHelicobacter pylori strains expresses Lewis antigens (Le^x, Le^y, Le^a, Le^b) which are similar to those expressed by gastric epithelial cells (“molecular mimicry”).1 In addition,H pylori LPS displays phase variation in these antigens—that is, the high frequency, reversible switching of phenotype2; for instance, a strain that expresses Le^x may yield variants that express Le^y. As yet, no definite role has been assigned to these Lewis antigens, nor to phase variation, in the pathogenesis of gastric disease.

In this issue of Gut (see page 18), Zheng and colleagues3 report that H pylori strains isolated from Asian peptic ulcer patients express two or more Lewis antigens more often than strains from non-ulcer dyspepsia patients (89.6 v 73.2%; p=0.035). What could be the link between H pylori …