Low mitogenic activity of synthetic lipid A analog, 2,3-acyloxyacylgalactosamine-4-phosphate, in cultured murine splenocytes.

The mitogenicity of chemically synthesized lipid A analogs, 2,3-acyloxyacylglucosamine-4-phosphate (A-103) and 2,3-acyloxyacylgalactosamine-4-phosphate (A-113), was compared. Synthetic lipid A analogs of the disaccharide-type (506), the monosaccharide-type (A-103) suspended in RPMI-1640 medium supplemented with triethylamine, and Salmonella typhimurium LT-2 lipopolysaccharide (LPS) were capable of increasing the incorporation of [3H]thymidine into splenocytes of C57BL/6 mice at various doses ranging from 1.0 to 100 micrograms/ml. However, the mitogenic activity of A-113 at these doses was markedly weaker than the activity of the above materials. When the A-103 and A-113 were suspended in RPMI-1640 medium supplemented with ethanol, the mitogenic activity of A-113 also showed lower activity than that of A-103 in the splenocytes of C57BL/6 mice. These findings indicate that the mitogenic activity of synthetic lipid A of the monosaccharide-type is affected by a kind of composed sugar.