DIFFERENTIAL ROLE OF INTERFERON-GAMMA IN THE POTENTIATING EFFECT OF MURAMYL PEPTIDES FOR ENHANCED RESPONSES TO LIPOPOLYSACCHARIDE IN MICE -EFFECT OF CYCLOSPORINE-A

Cyclosporin A (CsA) administration reduced mortality in mice sensitize d to endotoxic toxicity by various agents, such as muramyl dipeptide ( MDP) or a lipophilic derivative. CsA is an inhibitor of a variety of T cell responses, suggesting that muramyl peptides could influence LPS- induced effects via the release of lymphokine, The potentiation of TNF production by pretreatment with muramyl peptides was comparable in nu de mice and in controls, indicating that it is a T-independent mechani sm, and CsA produced a similar inhibition in both groups. Neutralizing antibody to IFN-gamma did not change the elevated TNF level obtained in the blood when LPS was given after a muramyl peptide, However, the same treatment with anti-IFN-gamma MAb prevented the death of mice cha llenged with LPS plus MDP or plus a lipophilic derivative displaying s imilar effects, In comparing three selected muramyl peptides, we also show that the priming effect could be dissociated from the toxic syner gism with LPS.