Immunosuppression induced by non-reducing acylated monosaccharide subunits of lipid A

Synthetic acylated glucosamine monosaccharides, representative of the non-reducing subunit of lipid A, were compared for their ability to induce non-specific suppression of antibody forming cells. Five of nine analogs were found to be functional in this respect, indicating that these compounds, carrying a phosphate at C4 and acyl substituents at C2 and C3 are the smallest synthetic analogs of lipid A capable of eleciting non-specific immunosuppression. A comparison of the analogs inducing suppression with those testing negative revealed that (i) a single 3-hydroxymyristoyl group at C2 is common to 4 5 analogs inducing suppression; (ii) addition of an oxytetradecanoyl group to the 3-hyroxymyristoyl group at either C2 or C3 negated suppression; and (iii) extreme specificity was exhibited in suppression induction such that substitution of either lauric (C₁₂) or palmitic (C₁₆) for myristic acid (C₁₄) at C2 voided transmission of the suppressive signal.