The Origin of the Synergistic Effect of Muramyl Dipeptide with Endotoxin and Peptidoglycan*

Co-incubation of human Mono Mac 6 cells with MDP and either LPS or peptidoglycan (PGN) resulted in an apparent synergistic effect on tumor necrosis factor-α (TNF-α) secretion, and it is suggested that MDP acts through receptor(s) other than those primarily responsible for transducing the effects of LPS and PGN.