Lipid A antiserum-mediated protection against lipopolysaccharide- and lipid A-induced fever and skin necrosis.

The antiendotoxic activity of lipid A antiserum was studied in rabbits, using lipid A (lipopolysaccharide)-induced fever and skin necrosis as test systems. It was found that lipid A antiserum had no significant antipyretic effect when it was incubated with lipid A or injected intravenously before lipid A challenge. However, in animals that were pretreated (day 0) with a single dose of lipid A (lipopolysaccharide), a significant protective effect of passively transferred antiserum (day 1) to lipid A (lipopolysaccharide fever) (day 2) was observed. Also, the lipid A (lipopolysaccharide)-induced local shwartzman reaction could be prevented by lipid A antiserum. In the fever system, the degree of protection depended on the preparative and the challenge doses as well as on the amount of antiserum transferred. The fever protection mediated by lipid A antiserum seemed to be lipid A (lipopolysaccharide) specific with regard to both the preparative and the challenge injections. Lipid A specificity of the protective factor present in the antiserum was indicated by the fauggest that the factor might be identical with lipid A-specific immunoglobulin. The significance of the preparative injection is not understood at the present time. Iti is concluded, however, that in the fever protection system described, besides specific humoral factors, other factors, perhaps cellular, are involved.