B cell activation and adjuvant activities of chemically synthesized analogues of the nonreducing sugar moiety of lipid A

Immunological activities of synthetic lipid A analogues (derivatives of 3‐O‐tet‐ radecanoyl D‐glucosamine) were investigated. Compounds possessing a N‐tet‐ radecanoyloxytetradecanoyl group with or without a 4‐O‐phosphoryl group exhibited both mitogenic and polyclonal B cell activating activities. Among these, the phos‐phorylated compound exhibited strong activity. 4‐O‐phosphorylated analogues with a N‐tetradecanoyl group or 6‐O‐tetradecanoyl group in addition to N‐3‐hydroxyacyl groups showed no activity. All the analogues tested showed adjuvant activity, which was determined by augmentation of IgM antibody response against sheep erythrocytes. Relationship between chemical structure and biological activities is also discussed.