Relation of structure to function in bacterial endotoxins. VIII. Biological activities in a polysaccharide-rich fraction.

This is the first report describing in vivo biologic activities elicited by a non-toxic, polysaccharide-rich, water soluble fraction obtained by partial acidic hydrolysis from endotoxic lipopolysaccharide. The two activities present in this preparation were a) mouse bone marrow cell colony formation stimulation (CSF) and b) protection of mice against lethal irradiation. With polysaccharide-deficient rough mutants of salmonella minnesota, the CSF-inducing activity could be restricted to the "core" region of the LPS structure. Sixty-minute hydrolysis with 1 N HCl at 100 degrees C or 0.1 M sodium metaperiodate oxidation at cold room temperature completely abolished CSF-inducing activity of the preparation, whereas it showed considerable resistance to mild alkaline hydrolysis. These findings indicate that the active component in this preparation is carbohydrate in nature. Lipid preparations from smooth LPS or from Re rough mutants are either much less active or completely inactive in the above two assays. The fully active polysaccharide rich preparation was found to be inert in seven other characteristic endotoxicity parameters.