SIMULTANEOUS EXPRESSION OF TYPE-1 AND TYPE-2 LEWIS BLOOD-GROUP ANTIGENS BY HELICOBACTER-PYLORI LIPOPOLYSACCHARIDES

Previous structural investigations performed on the lipopolysaccharide s (LPSs) from the human gastric pathogen Helicobacter pylori have reve aled that these cell surface glycan molecules express type 2 partially fucosylated, glucosylated, or galactosylated N-acetyllactosamine O an tigen chains (O-chains) of various lengths, which may or may not be te rminated at the nonreducing end by Lewis X (Le(x)) and/or Le(y) blood group epitopes in mimicry of human cell surface glycoconjugates and gl ycolipids, Subsequently, serological experiments with commercially ava ilable Lewis-specific monoclonal antibodies also have recognized the p resence of Le(x) and Le(y) blood group antigens in LI, pylori but, in addition, have indicated the presence of type 1 chain Le(a), Le(b), an d Le(d) (H-type 1) blood group epitopes in some H. pylori strains. To confirm their presence, structural studies and additional serological experiments mere undertaken on H., pylori strains suspected of carryin g type 1 chain epitopes, These investigations revealed that the O chai n region of H. pylori strain UA948 carried both Le(a) (type 1) and Le( x) (type 2) blood group determinants. The O-chain from H. pylori UA955 LPS expressed the terminal Lewis disaccharide (type 1 chain) and Le(x ) and Le(y) antigens (type 2), The O-chain of H. pylori J223 LPS carri ed the type 1 chain precursor Le(c), the H-l epitope (Le(d), type 1 ch ain) and an elongated nonfucosylated type 2 N-acetyllactosamine chain (i antigen). Thus, O-chains from H., pylori LPSs can also express fuco sylated type 1 sequences, and the LPS from a single H., pylori strain may carry O-chains with type 1 and 2 Lewis blood groups simultaneously . That monoclonal antibodies putatively specific for the Le(b) determi nant can detect glycan substructures (Le disaccharide, Le(c), and Le(d )) of Le(b) indicates their nonspecificity. The expression of both typ e 1 and 2 Lewis antigens by H. pylori LPSs mimics the cell surface gly comolecules present in both the gastric superficial (which expresses m ainly type 1 determinants) and the superficial and glandular epitheliu m regions (both of which express predominantly type 2 determinants). T herefore, each H., pylori strain may have a different niche within the gastric mucosa, and each individual LPS blood group antigen may have a dissimilar role in H. pylori adaptation.