Failure of monoclonal antibodies to core glycolipid to bind intact smooth strains of Escherichia coli.

To study the ability of antibody to the core glycolipid (CGL) region of lipopolysaccharide (LPS) to bind intact gram-negative bacterial cells, we produced monoclonal antibodies that bind LPS from the Escherichia coli rough mutant J5. Four representative monoclonal antibodies that bound four distinct epitopes on the CGL region of LPS were studied. All four antibodies bound both isolated J5 LPS and intact J5 bacterial cells, but none of the antibodies bound to intact cells of E. coli O111:B4 or K1:O7. Binding of the monoclonal antibodies to isolated LPS from these latter two smooth strains was variable. These results confirm the presence of shared antigenic sites in the CGL region of heterologous LPS molecules but indicate that these sites are not necessarily available on smooth gram-negative bacteria for binding by antibody to CGL.