Involvement of a Chemical Moiety of Bacterial Lipopolysaccharide in Production of Interferon in Animals

Abstract

Interferon is released in mice that receive an injection of the lipopolysaccharide (LPS) of Salmonella typhimurium (strain LT-2), glycolipids from organisms of Rb and Re chemotypes, or lipid A. No interferon is released by O-antigenic hapten lacking the glycolipid moiety. The interferon-releasing ability of glycolipid from the Re chemotype is reduced by partial hydrolysis with acid, which removes 2keto-3-deoxy-octonic acid and reduces the solubility of the hydrolyzed product. The ability of the glycolipid to release interferon is increased by partial hydrolysis with alkali. This treatment removes some of the fatty acids but little or no 2-keto-3-deoxy-octonic acid and increases the solubility of the hydrolyzed product; interferon-releasing ability is progressively reduced with more extensive hydrolysis and concomitant loss of fatty acids. The interferon-releasing ability of unhydrolyzed glycolipid is markedly increased by complexing with bovine serum albumin. These results show that the interferon-releasing property of LPS resides in the lipid A portion of the molecule. Furthermore, the relative solubility and the presence of fatty acids in LPS and its derivatives play a decisive role in their ability to release interferon.