Macrophage activation by muramyl dipeptide as measured by macrophage spreading and attachment.

A synthetic bacterial cell wall constituent, muramyl dipeptide (MDP), was found to induce the enhancement of macrophge spreading and attachment on glass or plastic surfaces. Macrophages exposed to bacterial lipopolysaccharide or lymphokine-containing cell supernatants showed similar enhancement. This finding supports the view that MDP activates macrophages. MDP was also found to enhance the viability of macrophages but to inhibit 3H-thymidine incorporation by macrophages.