Donor-dependent Stimulation of Superoxide Output by Muramyl Dipeptide (MDP) in Human Granulocytes and Synergism of MDP with Lipopolysaccharide

In the course of an investigation we observed: (1) a donor- dependent stimulation of the superoxide output by MDP and thus, this compound must be characterized as active in this respect. MDP activated mainly the second phase of the superoxide output; (2) no beneficial effect of a preincubation ("priming") with MDP prior to the addition of a second challenge (e.g., LPS). That means, preincubation with MDP did not lead to a higher superoxide production with endotoxin. Controls, preincubated with buffer instead of MDP showed the same superoxide output; thus, chemiluminescence counts might increase without a "priming" compound as well; (3) a synergism between MDP and LPS. The superoxide output was significantly higher when both substances were added simultaneously than when they were applied alone.