Modulation of lymphocyte activating factor activity (interleukin 1 like activity) and acute phase proteins in pertussis-induced air pouch inflammation by muramyl dipeptide.

We have studied the effect of the macrophage activator, muramyl dipeptide (MDP) on immune inflammation induced in the rat six day subcutaneous air pouch. Treated animals received either 100 micrograms or 200 micrograms MDP at the time of challenge and twenty four hours before exudate harvest. Using the thymocyte co-mitogenic assay for lymphocyte activating factor (LAF), 100 micrograms MDP enhanced LAF activity whereas 200 micrograms caused inhibition. Increased dilution of 200 micrograms exudate in this assay removed this inhibition. Similarly, at the lower dose, MDP caused enhanced production of the acute phase protein alpha 1 glycoprotein, whereas the higher dose had no effect. The present study suggests that macrophage activity can be manipulated in vivo to produce LAF and naturally occurring inhibitors of LAF. These studies indicate that the stimulation of LAF inhibitors by MDP may be a potential therapeutic action.