Refined detoxified endotoxin

A method of producing an adjuvant response or stimulating the immune response of a warm blooded animal comprising injecting into said warm blooded animal an effective amount of a composition comprising refined detoxified endotoxin having no detectable 2-keto-deoxyoctanoate, between about 350 and 475 n moles/mg of phosphorus and between about 1700 and 2000 n moles/mg of fatty acids, in combination with a pharmaceutically acceptable carrier, said refined detoxified endotoxin having been prepared by the steps of:

• (a) hydrolyzing an endotoxin extract obtained from microorganisms of the Family Enterobacteriaciae with an inorganic or organic acid;
• (b) lyophilizing the hydrolyzed product to obtain crude lipid A;
• (c) treating crude lipid A with a first solvent capable of dissolving fatty acids and impurities without dissolving said crude lipid A;
• (d) dissolving the resulting insoluble product in a second solvent in which said crude lipid A is soluble;
• and
• (e) passing the resulting solution through a chromatographic column to obtain the desired refined detoxified endotoxin.