These associations remained relatively unstudied until Borén et al. suggested that the Leb antigen of the Lewis blood group system acts as a receptor for H. pylori on the gastric mucosa.12 The Leb antigen is a oligosaccharide rich in fucose molecules and is expressed in greater quantities in the O blood group.13,14 Borén et al. investigated the hypothesis that, due to the presence of fucose molecules in the Leb antigen, the carriers of the O blood group would have a greater tendency towards infection by H. pylori. Here, MUC5AC is linked to infection.