Preparation and Properties of Antisera against the Lipid‐A component of Bacterial Lipopolysaccharides

Abstract

The lipid‐A component of lipopolysaccharides, when presented in a suitable form, acts as an immunogen in rabbits, giving rise to the production of circulating antibodies. Highest anti‐lipid‐A titers were obtained on immunization with acid‐treated bacterial cells coated with lipid A. Anti‐lipid‐A activity of the immune sera could be assayed by passive hemolysis of lipid‐A‐sensitized erythrocytes in the presence of complement. On filtration of the immune globulins on Sephadex G‐200, antibodies against lipid A were detected in the IgM and IgG fractions. Lipid A preparations derived from various Salmonella and one Echerichica coli strain exhibited strong serological cross reactions with anti‐lipid‐A antisera. Furthermore, lipid‐A antiserum also cross‐reacted with all lipopolysaccharides tested, although in some cases to a low degree. On the other hand, only 8 out of 13 antibacterial antisera interacted with lipid‐A‐coated red cells. Finally, it was found that anti‐lipid‐A antibodies are effective in sensitizing E. coli 0111 bacteria for intraperitoneal phagocytosis.