Lipophilic derivative of muramyl dipeptide is more active than muramyl dipeptide in priming macrophages to release superoxide anion.

Mouse peritoneal macrophages, when treated with a lipophilic derivative of muramyl dipeptide either in vitro or in vivo by intraperitoneal injection, showed a more than fivefold increase in their ability to generate superoxide anion after stimulation of the macrophages with phorbol myristate acetate. This response was more than twice that observed with the parent molecule, muramyl dipeptide (MDP). Unlike MDP, which has a systemic effect, the lipophilic derivative, [B30]-MDP, did not alter the response of peritoneal macrophages when given subcutaneously in the flank, suggesting that [B30]-MDP remains localized at the site of injection. The enhanced effect of [B30]-MDP over MDP appeared to be due to the inherent lipophilicity of the molecule, and was probably not due to either stimulation of T lymphocytes or activation of the alternative pathway of complement.